半導體異質結構一致和非一致自旋相依傳輸(III)

行政院國家科學委員會專題研究計畫 成果報告

半導體異質結構一致和非一致自旋相依傳輸(3/3)

中 華 民 國 94 年 10 月 24 日

摘要 (Abstract ) 英文

Studies of spin-dependent confinement and transport phenomena in semiconductor nano-structures have been progressing significantly since spintronics became a focus of recent interest. The most promising application of spintronic devices can be found in the potential applications for quantum information processing, and, in particular, in the design of a spin-based quantum computer. For the recent years in our pioneering works we proposed to deploy the spin-orbit interaction in conventional non-magnetic III-V semiconductor nano-structures to build elements of spintronic devices. In III-V and II-VI semiconductors the spin-orbit interaction lifts the conduction state spin-degeneracy and has been used successfully to interpret experimental results in various semiconductor nano-structures: quantum wells, wires, nano-rings, and dots. The semiconductor approach has the advantage of being compatible with conventional semiconductor technology.

This report summarizes the major results obtained from the program of the “Coherent and non-coherent spin-dependent transport in semiconductor heterostructures” project. Three subjects are discussed in the following including: spin-dependent coherent transmission probability and tunneling time for all-semiconductor symmetric double barrier structures; spin-dependent scattering and the spin-spin-dependent Hall effect in three-dimensional random arrays of small semiconductor quantum dots and from impurities in two-dimensional channels; magnetic properties of semiconductor multi-electron quantum dots and rings. In addition we investigated magneto-optical properties of semiconductor nano-structured meta-materials built from non-magnetic InAs/GaAs nano-rings. Those systems can exhibit simultaneously negative effective permittivity and permeability over a certain optical frequency range – the main condition for materials with negative refractive index.

Several publications were performed based on those results.

中文 因為自旋電子學近來備受矚目，所以在半導體奈米結構中，電子自旋的侷限效應與 傳輸現象的研究有很突破的進展。自旋電子元件中最具潛力與可行性的應用當屬量子資 訊方面，特別是在自旋量子電腦的設計。近年來我們進行很多具有首創性的研究，研究 傳統非磁性 III-V 族半導體奈米結構的自旋軌域的交互作用，以建立自旋電子元件的基本 要素。在 III-V 族和 II-VI 族半導體中，自旋軌域的交互作用提升了傳導帶自旋能階簡 併，這個結果成功的解釋了各種不同半導體奈米結構的實驗結果，例如：量子井、量子 線、量子環與量子點。而且這個半導體理論具有可以跟傳統半導體科技相容的優點。 這份報告總結的主要結論都是從”半導體異質結構的同調與非同調自旋相依傳輸”的研 究計劃歸納出來的。我們主要探討三個主題：在各種半導體中，對稱雙能障結構的自旋 相依同調傳輸的機率與穿遂時間；分別探討三維隨機排列的半導體量子點與二維通道內 的雜質，造成的自旋相依散射與自旋相依霍爾效應；具有多電子的半導體量子點與量子 環，其磁性特性。另外，我們也研究由非磁性的砷化銦/砷化鎵奈米環組成的奈米結構半 導體的磁性與光性。這個系統可以在一個特定的光之頻率範圍內，同時表現出負的有效 介電常數與導磁率特性 (主要的條件是材料本身必須具有負的折射率)。 我們的研究成果已經有數個發表在期刊上。 關鍵詞: 自旋電子 學 ; 自旋 ; 奈米結構 ; 半導體

Contents 1. 2. 3. 4. 5. 6. 7. 8. Introduction

Spin-dependent coherent transmission in all-semiconductor symmetric double barrier structures

2.1 Electron spin filtering in all-semiconductor tunneling structures

2.2 Time-resolved spin-filtering in semiconductor symmetric resonant barrier structures

2.3 Main results and discussion

Spin-dependent scattering and the spin-dependent Hall effect

3.1 Spin-dependent electron single and double scattering from quantum dots and anti dots

3.2 Spin-orbit interaction and electron scattering from impurities in quantum well

3.3 Spin-dependent Hall effect in semiconductor quantum wells 3.4 Main results and discussion

Magnetic properties of semiconductor quantum dots and rings

4.1 Magnetic properties of parabolic quantum dots in presents of the spin-orbit interaction

4.2 Main results and discussion

Nano-structured meta-materials built from non-magnetic InAs/GaAs nanorings 5.1 Magneto-optical response of layers of semiconductor quantum dots and

nano-rings

5.2 Left handed composite materials in the optical range 5.3 Main results and discussion

Self evaluations List of publications

List of thesis’s of graduated students

4 6 7 13 18 19 20 25 33 39 41 42 47 49 50 62 65 66 68 70

1. Introduction

In order to utilize spin in semiconductor nano-structures, one needs to be able to polarize, inject, transport, manipulate, store, and detect spin. That can make use in modern quantum information, quantum cryptography, and quantum computing.

All of the needs necessarily require comprehensive quantitative understanding of the physical processes controlling the electron spin in quantum semiconductor nano-structures. To manufacture spintronics applications a large number of investigations need to be performed:

- explore transport, optical and magnetic properties of semiconductor nano-structures with promising spin dependent properties;

- understand and control spin dependent interface effects and spin dependent transport across semiconductor interface and in multiple quantum well structures;

- explore issues in controlling spin optical, magnetic, optical, and magneto-transport effects in quantum dots, arrays of quantum dots, antidotes and quantum wells and wires as well.

Structures of interest

Semiconductor quantum nano-structures (quantum wells, dots, antidots, and rings) on the base of semiconductors with strong electron spin-orbit interaction InAs/GaAs, InAs/Si, InSb/(GaAs, InAs, GaSb, InP).

Phenomena, properties and characteristics of semiconductor quantum structures under investigation

1. Time dependent characteristics of tunneling and transport with quantum spin states within natural frequency scale given by spin splitting (GHz-THz). Spin dependent resonant tunneling and spin filtering in multi-layer semiconductor structures.

2. Spin dependent transport and characteristics of electron scattering in antidot arrays and impurities in semiconductor quantum wells.

3. Optical (infrared absorption and magneto photoluminescence) characteristics of semiconductor quantum nano-structures (quantum wells, dots, and rings).

4. Spin dependent transport and characteristics to implement the “spin field-effect transistor” or the “spin high electron mobility transistor”.

5. Magnetic characteristics (magnetization of single and multi-electron quantum dots and rings). 6. Magnetic and magneto-optics characteristics of quantum dot’s and ring’s arrays.

Theoretical problems must be solved

1. Spin dependent electron transport in semiconductor quantum nano-structures:

- spin dependent tunnel and spin dependent quasi ballistic electron transport in multi-barrier structures;

- spin dependent electron transport in arrays of quantum dots (antidots) with external electric and magnetic fields, and different mechanisms of the electron scattering in semiconductor quantum wells.

2. Spin dependent electron confinement in small semiconductor quantum dots and nano-rings: - electron spin state characteristics for various types of small quantum dots and rings of

semiconductors with strong spin-orbit interaction;

- electron spin states in small semiconductor quantum dots and rings in external magnetic fields;

3. Spin dependent optical and magnetic phenomena in semiconductor quantum rings: - Magneto-optical and luminescence spectra of semiconductor quantum nano-rings; - effects of trapped magnetic flux interaction with electron spin in small quantum rings; - optical characteristics of two and three dimensional arrays of them.

Exactly like it is mentioned above we performed the program of theoretical research, which results we present in this report.

2. Spin-dependent coherent transmission in all-semiconductor symmetric double barrier structures

2.3 Main results and discussion

For the reason of spintonics development the electronic spin polarization (filtering) in solid-state systems has attracted considerable attention. Many possible structures were investigated to reach high level electronic spin filtering and injection. Most of them consist of magnetic material elements. But in principle one can use the all- semiconductor approach utilizing multi-layered nano-systems to generate and detect the electron spin polarization. The semiconductor approach has the advantage of being compatible with conventional semiconductor technology. From this point of view the most important property of semiconductors to be utilized in all semiconductor spintronic nano-devices is the spin-orbit (SO) interaction. The control of spin in semiconductors together with modern semiconductor technology can guarantee the future of the spintronics and result a valuable commercial interest.

In the bulk of III-V and II-VI semiconductor materials the SO interaction lifts the spin-degeneracy of the conduction states in the center of the Brillouin zone. This part of the SO interaction is called the bulk inversion asymmetry (BIA) type and it is presented by the effective Dresselhaus Hamiltonian. Macroscopic effective electric fields in semiconductor nano-structures result the structural inversion asymmetry (SIA) and a linear (on the electron wave-vector k) term (or the Rashba type) of the SO interaction. It has been found out recently by us that the Rashba spin-orbit coupling in conventional III-V semiconductor tunnel barrier structures can lead to the spin-dependent tunneling phenomenon. The spin-polarization ratio in tunneling structures is defined as , , where T±

(

)

the part of the electronic energy which corresponds to the perpendicular motion to the barrier (z-axis), and k=(k_x,k_y) is parallel to the barrier component of the electronic wave vector. In symmetric structures with the exceptional Rashba interaction included we need to apply an external perpendicular electric field Fz to generate the asymmetry of the tunneling probability. In

the same time asymmetric structures the difference between T₊and T₋ exists with zero external electric field and there is a possibility to reverse the polarization by means of the change of the external electric field Fz. We further investigated spin-dependent tunneling probability for

realistic symmetric tunneling structures with account both the Rashba and Dresselhaus couplings. Our calculation is performed for realistic semiconductor structures on the base of the effective electronic one band Hamiltonian, energy and position dependent electron effective mass approximation, and spin-dependent Ben Daniel-Duke boundary conditions. We demonstrated that the transmission tunneling probability for a realistic symmetric single barrier structure can gain a well recognizable spin dependence for not too large in-plane wave vector of tunneling electrons. In addition one can control the magnitude of the polarization ratio by external electric field. The described effect can be a base for more advanced spin-filtering techniques at zero magnetic field. Our calculation results show that interplay between BIA and SIA interactions makes the spin filtering processes more rich and controllable.

The tunneling time is a basic characteristic that determines the dynamic range of tunneling devices. Based on the stationary phase concept and the effective one-band Hamiltonian with the Dresselhaus spin-orbit coupling, we obtained numerical results on the tunneling time trough a realistic InGaAs/InAlAs/InGaAs resonant symmetric structure. It was shown that the polarization efficiency of the structure has a well defined resonance behavior that can lead to a considerable spin polarization of electrons tunneling trough the structure. In the low energy region, the ratio between the tunneling times of electrons with opposite spin orientation can reach a few orders in magnitude. The results indicate that the Dresselhaus spin-orbit coupling separates the time dependent response for electrons tunneling with different spin polarizations. Further the large and tunable ratio of the tunneling times provides a possible way to construct a dynamic spin filter. The characteristic time of such devices have also been estimated and presented as a simple functional dependence on the barrier and well width. The relation between the delay time and the width is simple and can be used as a design rule to select working frequencies of spintronic devices.

( ) (₍ )₎ (₍ )₎ k k k k k , , , , , P z z z z z E T E T E T E T E − + − + + − =

3.4 Main results and discussion

In semiconductors the most important interaction, which causes spin-dependent processes is the spin-orbit interaction. The Rashba spin-orbit coupling is an essential element of the proposed by Datta and Das the spin field effect transistor. A new branch of semiconductor electronics so called spintronics became under an extensive development recently. For this reason, the spin dependent kinetics of electrons in traditional III-V semiconductor heterostructures becomes a topic of a great interest from theoretical and practical points of view. Our study deals with a model of the spin-dependent electron scattering from nano-scale semiconductor quantum dots (antidots). Recent advances in semiconductor nano-technology allow us to consider small spherical dots (antidots) of III-V semiconductors as “artificial defects” with controllable parameters. We calculated the polarization (the Sherman function) after a single scattering and than investigate how the polarization changes after the second scattering. The one electron band effective Hamiltonian and the spin dependent boundary conditions for spherical quantum dots (antidots) allowed us to calculate a spin asymmetry in the electron scattering cross-section. We found a polarization produced by single and double scattering of unpolirazed electron beams because by the spin-orbit interaction. We would like to stress that, the polarization is caused by non-magnetic GaAs/InAs semiconductor structures without external magnetic fields. We should mention that in the Anomalous Hall effect the Hall angle is proportional to the Sherman function at the Fermi energy shell. Our calculation results for three-dimensional random arrays of small semiconductor quantum dots (antidotes) suggest a small but measurable magnitude of the angle for antidotes. The anomalous Hall effect produced by quantum antidots is expected to be reduced by the electron impurity scattering, but should still have a significant magnitude. This effect is potentially useful in integrated electron spin-polarization devices based on all-semiconductor heterostructures.

In two-dimensional quantum wells, the spin-dependence of the scattering processes is expected to be stronger than in the bulk because of the localization of electrons' wave-functions in the conduction channel and well known peculiarities in the two-dimensional electron elastic scattering cross section. It should be noted, that the problem remains complicated even for a simplest two-dimensional electron motion because in general the spin-orbit interaction should be described by a three-dimensional model.

Using the delta-doping technique, the Coulomb attractive and repulsive impurities can be precisely placed in heterostructures. It allows us to model theoretically the effect the spin-dependent scattering from the impurities located inside or outside the conductive channel. Most of the theoretical simulations of two-dimensional electron elastic scattering processes from the impurities were conducted in details in the first Born approximation. However, it is well known, when the perturbation theory is used, the dependence on spin in the elastic cross section appears only in the approximation that follows the first Born approximation. For this reason, we used in our calculations of the spin-dependent scattering cross-section the partial wave approach, which was also used in some simulations of the spin-independent elastic scattering cross-section when the first Born approximation is not applicable. In this study we calculated the spin-dependent elastic scattering cross-section for electrons scattered by impurities in two-dimensional heterostructures of III-V semiconductors. We used the effective one band Hamiltonian with the Ben-Daniel-Duke boundary conditions for electronic envelop-functions to calculate the spin-dependent elastic cross-section for electrons scattered from screened repulsive and attractive isolated impurities with the spin-orbit coupling. The impurities are located inside the quantum well. The one electron band effective Hamiltonian and Rashba model of the spin-orbit interaction allow us to calculate the left-right asymmetry in the electron scattering cross-section. We have found a large spin-dependent asymmetry in the elastic cross-section for electrons

Hall effect measurements. This effect is potentially useful in integrated electron spin-polarization devices based on semiconductor heterostructures. It also can be used as a tool of determination of spin coupling parameters in III-V narrow gap semiconductor heterostructures.

We calculated contributions from the skew-scattering (SS) and side-jump (SJ) mechanisms to the spin-dependent Hall effect (SDHE). Our calculation is based on the effective one band Hamiltonian and Rashba type model of the orbit interaction. We have found large spin-dependent Hall angles (SDHA) for AlInAs/InGaAsAs/AlInAs and CdTe/InSb/CdTe symmetrical quantum wells. For instance, in the CdTe/InSb/CdTe narrow quantum wells SDHA can reach 2.5x10-3 rad. This could be detected in the measurements of the Hall effect at low temperatures and this is potentially useful in integrated electron spin-polarization devices based on semiconductor heterostructures. It also can be used as a tool of determination of spin coupling parameters in III-V narrow gap semiconductor heterostructures. We suggest that experimental investigations should be conducted to verify our theory predictions.

4.2 Main results and discussion

We calculated the magnetization and susceptibility of a cylindrical quantum dot with the parabolic confinement potential for electrons when the spin-orbit interaction is included into consideration. Application of a magnetic field along the dot axes generates a complicated structure of the electron energy levels and the theoretical analysis of the parabolic quantum dots in magnetic fields achieves a rich physics. Recently the well pronounced spin-splitting was found by us for the parabolic confinement potential model of semiconductor quantum dots with parameters of InSb and InAs. The spin-splitting at zero magnetic field leads to a crossing of the energy levels in weak external magnetic fields (similarly to the general Paschen-Back effect) and can provide unusual magnetic properties of the quantum dots.

The magnetization for the same number of electrons with and without the spin-orbit interaction is also presented. The magnetization calculated without the spin-orbit interaction demonstrates a clear shell filling behavior: for N=2,6 (closed shells) the magnetic momentum are canceled out at B=0; for N=1,3,4,5 (partially occupied shells) the magnetization takes a positive value at B=0. Our calculation results suggest that the spin-orbit interaction keeps the cancellation for the closed shells and slightly changes the magnetization for N=1,3. The most interesting result we obtain for dots with four and five electrons. The spin-orbit splitting partially lifts up the degeneracy of levels and changes the electron structure. This assures the magnetization to be zero at B=0 for dots with four electrons in contrast to the case without the spin-orbit interaction. The crossing between levels for the quantum dot with four electrons produces a sharp jump in the magnetization and shifts the magnetic susceptibility peak. For the quantum dot with five electrons the jump reflects the crossing between another levels for a higher magnetic field and generates an additional (in comparison to the case with absent of the spin-orbit interaction) peak for the magnetic susceptibility. One can control the spin coupling parameters in planar semiconductor systems by means of external or build-in electric fields. By variations of the fields one can change magnitudes of the parameters. From the above it appears that the peaks of the magnetic susceptibility which are generated by the spin-orbit interaction should have the following interesting properties. It is possible to perform a switching between the configuration with and without spin-orbit interaction by means of the external electric field or the design of quantum dots.

The spin-orbit (SO) interaction in narrow-gap semiconductor quantum dots has been the object of extensive investigations recently. It links the spin and the charge dynamics and opens up the possibility of spin control by means of electric fields in non-magnetic structures. It was found that SO coupling can sufficiently change magnetic properties, far-infrared absorption, and spin relaxation rate in quantum dots. In this work we extended our previous calculations and employ the Local Spin Density Approximation to investigate ground state magnetic properties and addition energy spectra for few electron InSb parabolic quantum dots with strong SO coupling. We consider SO interaction in semiconductor cylindrical quantum dots with a quasi-two-dimensional parabolic confinement for electrons. The addition energy is defined like the following: Eadd(N) = Edot(N + 1) − Edot(N), where Edot is total ground state energy of electronic system and N is the number of electrons in the dot. Magnetic field is applied along the dot axes generates a complicated structure of the electron energy levels. The addition energy spectrum shows for a small InSb parabolic quantum dot (effective radius ~ 15 nm) with and without including of SO interaction. The SO interaction in combination with weak magnetic fields can break the conventional sequence of “magic numbers” (N=2, 4, 6…) for the lowest stable electronic levels. The lover panel in the figure demonstrates the phenomenon – for the quantum dot with 3 electrons the addition energy is larger than that for 4 electrons. This property can be controlled by an external electric field.

changes of the magnetization and susceptibility at low magnetic fields are attributed to the crossing between the spin-split electron levels in the energy spectrum. Detailed calculation using parameters of InSb semiconductor quantum ring demonstrates an altering in magnetic properties of the ring: from diamagnetic to paramagnetic. We proposed an additional possibility to control the effect magnitude by external electric fields or design of the rings.

5.3 Main results and discussion

We studied theoretically the magneto-optical response functions (like polarizability and absorbance) for semiconductor quantum dots and nano-rings, when they are arranged in a square lattice. The calculations clearly show that rings are more effective to exploit the response from magnetic fields than dots. Despite a lower volume fraction ring structures have stronger variation of absorbance when the magnetic field changes than the dots. We have shown that layers of InAs/GaAs self-assembled nano-rings exhibit the optical AB effect particularly in reflectance mode. While AB effects are discussed in the literature for the cases of infrared absorption and photoluminescent emission, we can expect this behavior to be observable in ellipsometric measurements with good resolution. The calculated results suggest large polarization anisotropy for absorbance at large angles of incidence. This can be measured and should display the new optical AB effects for low temperature and moderate magnetic field regimes. Actual magnitude of the effect should be verified both by experiment and by more sophisticated calculations.

Left handed composite materials (LHCMs) exhibit simultaneously negative permittivity and permeability over a certain frequency range. It is acknowledged that LHCMs can have a variety of exciting applications. A particularly important and challenging problem in this field is the realization of LHCMs in the optical frequency range. A negative refractive index was confirmed in the GHz and THz range many years after its theoretical prediction, but most of magnetic materials at frequencies in the GHz range and above have a magnetic response which is tailing off.

In this our work we show theoretically that there is an opportunity to obtain negative permittivity and magnetic permeability simultaneously in the optical range by using nano-structured composite semiconductor materials. One of the problems arising in LHCMs for the optical range is that the size of the structural elements has to be of nanometer scale. Another problem is that the use of conductive elements is inappropriate because of the high losses. Semiconductor nano-rings are ideal building blocks and could meet the requirements mentioned. It is necessary to emphasize that structural elements possessing magnetic response, have sizes much smaller than the operating wavelength and the composite materials made from them can be characterized by effective permittivity and magnetic permeability only.

In this study we have shown that for three-dimensional photonic structures based on an artificial lattice of InAs/GaAS nano-rings the effective permittivity can be negative in the optical range. At the same time the frequency domain with the negative permittivity and magnetic permeability can be tuned by changing the individual capacity of the rings. These results could be particularly useful for design of a new class of left handed composite materials in the optical range.

6. Self-evaluation

In the project which results reported we investigated deploying of the spin-orbit interaction in conventional non-magnetic III-V semiconductor nano-structures to build elements of spintronic devices. The semiconductor approach has the advantage of being compatible with conventional semiconductor technology. It has been demonstrated theoretically that the structures can be efficiently used to polarize, inject, transport, manipulate, store, and detect electron spins. Our results suggest to exploit spin-orbit interaction in semiconductor nano-structures for spintronics needs.

#1. It has been proposed that in tunnel barrier structures the spin-orbit interaction can lead to the

spin-filtering. In resonant tunnel heterostructures (due to the strict resonant tunnel conditions) the spin-filtering can gain a higher level without an additional magnetic field and can be controlled by external electric fields even in symmetrical structures. This idea attracted much interest in publications of other authors and it is an important enhancement of or previous pioneering works in a new branch of spin-dependent investigation in all semiconductor structures – spin-filtering without magnetic elements. Those results are published in the leading international journals, appreciated by the scientific society and citied.

#2. We introduced a model of the spin dependent electron scattering from an array of nano-scale

all semiconductor quantum dots (antidots) - “artificial defects”. We found theoretically for the first time that the differential cross-section for InAs/GaAs antidots demonstrates a relatively large left-right asymmetry in scattering cross-section. We described theoretically the Anomalous Hall effect appeared in three-dimensional random arrays of small semiconductor quantum dots and due to spin-dependent scattering from impurities in two-dimensional channels as well. In semiconductor quantum wells the effect of the spin-orbit interaction on the processes of electron’s scattering appears to more stronger that in the bulk. This is a result of the localization of electrons' wave-functions in the conduction channel. The one-electronic-band effective Hamiltonian and spin-orbit coupling potential of the impurities allowed us to formulate and solve for the first time the 2-D spin-dependent Boltzmann equation and to calculate the spin-dependent Hall angle at zero magnetic field. We have found large spin-dependent Hall angles for AlInAs/InGaAsAs/AlInAs and CdTe/InSb/CdTe symmetrical quantum wells. This could be detected in the measurements of the Hall effect at low temperatures and this is potentially useful in integrated electron spin-polarization devices based on all-semiconductor heterostructures. It also can be used as a tool of determination of spin coupling parameters in III-V narrow gap semiconductor heterostructures. We suggest that experimental investigations should be conducted to verify our theory predictions. Several publications in leading international journals were performed based on the results. The publications are appreciated by the scientific society and citied.

.

#3. We found that a significant spin-splitting in the electron energy spectrum in semiconductor

quantum dots and nano-rings at zero magnetic field and the state crossing with external magnetic. The crossing of electron energy levels with different spins leads to unusual magnetic properties of quantum dots and an additional degree of freedom for the electron spin state (qubit) manipulation in quantum dots. We calculated the magnetization and susceptibility of a cylindrical quantum dot with the parabolic confinement potential for electrons when the spin-orbit interaction is included into consideration. Application of a magnetic field along the dot axes generates a complicated structure of the electron energy levels and the theoretical analysis of the parabolic quantum dots in magnetic fields achieves a rich physics. The well pronounced spin-splitting was found by us for the parabolic confinement potential model of semiconductor quantum dots with parameters of InSb and InAs. The spin-splitting at zero magnetic field leads to a crossing of the energy levels in weak external magnetic fields (similarly to the general

Paschen-Back effect) and can provide unusual magnetic properties of the quantum dots. Results of those works are also appreciated and citied.

#4. In view of possible nano-scale semiconductor spintronic device and quantum computing

implementations, we investigated in detail the quantized energy structures and magnetic properties of a new semiconductor nano-object - quantum nano-ring. We have shown that layers of InAs/GaAs self-assembled nano-rings exhibit a new types of the optical Aharonow-Bohm effect particularly in reflectance mode. While AB effects are discussed in the literature for the cases of infrared absorption and photoluminescent emission, we predicted this behavior to be observable in ellipsometric measurements with good resolution. The calculated results suggest large polarization anisotropy for absorbance at large angles of incidence. This can be measured and should display the new optical AB effects for low temperature and moderate magnetic field regimes. We have shown for the first time that for three-dimensional photonic structures based on an artificial lattice of InAs/GaAS nano-rings the effective permittivity can be negative in the optical range. At the same time the frequency domain with the negative permittivity and permeability can be tuned by changing the individual capacity of the rings. These results could be particularly useful for design of a new class of left handed composite materials in the optical range.

7. List of publications

Referred papers:

1. Edward Chen, O.Voskoboynikov, C. P. Lee, “Spin-dependent electron single and double scattering from quantum dots and antidotes”, Solid state communications, vol. 125, no. 7-8, pp. 381-385, Feb. 2003.(SCI)

2. H. C. Huang, O.Voskoboynikov, and C. P. Lee, “Spin-orbit interaction and electron elastic scattering from impurities in quantum wells”, Physical Review B, vol. 67, no.19, pp. 195337-1-8, May 2003.(SCI)

3. H. C. Huang, O.Voskoboynikov, and C. P. Lee, “Role of the spin-orbit interaction in elastic scattering of electrons in quantum wells”, Microelectronics Journal, vol. 34, no. 5-8, pp. 687-690, Aug. 2003.(SCI)

4. O.Voskoboynikov, O. Bauga, C. P. Lee, and O. Tretyak, “Magnetic properties of parabolic quantum dots in the presence of the spin-orbit interaction”, Journal of Applied Physics, vol. 94, no. 9, pp. 5891-5895, Nov. 2003.(SCI)

5. H. C. Huang, O.Voskoboynikov, and C. P. Lee, “Spin-dependent Hall effect in semiconductor quantum wells”, Journal of Applied Physics, vol. 95, no. 4, pp. 1918-1923, Feb. 2004.(SCI)

6. Leo Yu and O.Voskoboynikov, “Electron spin filtering in all-semiconductor tunneling”, Superlattices and Microstructure, vol. 34, no. 1-2 , pp. 547-552, Aug. 2004. (SCI)

7. O.Voskoboynikov, G. Dyankov, C. M. J. Wijers, “Left Handed Composite Materials in the Optical Range”, Microelectronics Journal, vol. 36, no. 1, pp. 564-566, May. 2005. (SCI).

8. O.Voskoboynikov, C. M. J. Wijers, J.J. Liu, and C.P. Lee, “Interband magneto-optical transitions in a layer of semi-conductor nano-rings”, Europhysical Letter, vol. 70, no. 5, pp. 656-662, Jun. 2005. (SCI).

9. O.Voskoboynikov, C. M. J. Wijers, J.J. Liu, and C.P. Lee, “The Magneto-Optical Response of Layers of Semiconductor Quantum Dots and Nano-Rings”, Physical Review B, vol. 71, no. 24, pp. 245332-1-12, Jun. 2005. (SCI).

10.Leo Yu and O. Voskoboynikov, “Time resolved spin-filtering in semiconductor symmetric resonant barrier structures”, Journal of Apply Physics, vol. 98, no. 2, pp. 023716-1-5, Jul. 2005. (SCI).

11.O.Voskoboynikov, C. M. J. Wijers, J.J. Liu, and C.P. Lee, “Magneto-optics of layers of semiconductor quantum dots and nano-rings”,Brazlian Physical Journal, accepted, to appear in August 2005.

12.O. Bauzha, O.Voskoboynikov, O. Tretyak, “Influence of spin-orbit interaction on magnetization of quantum dots”, accepted to appear in Bulletin of the University of Kiev. Series Physics and mathematics (2005).

quantum rings with spin-orbit interaction”, submitted to Ukrainian Physical Journal (2005).

Conference abstracts:

1. O.Voskoboynikov, and C. P. Lee, “Electron spin filtering in all-semiconductor tunnel structures”, International conference on narrow gap semiconductors (NSG-11), Buffalo, USA, June 16-20, 2003.

2. Leo Yu, H. C. Huang and O.Voskoboynikov, “The Dresselhause and Rashba Spin-Orbit Interactions and Spin Filtering”, The International Symposium on Functional Semiconductor Nanosystems (FSNS2003), Atsugi, Japan, November 12-14, 2003.

3. Leo Yu and O.Voskoboynikov “Electron spin filtering in all-semiconductor tunneling”, Sixth International Conference on New Phenomena in Mesoscopic Structures and Fourth International Conference on Surfaces and Interfaces of Mesoscopic Devices, Maui, Hawaii, U.S.A., November 30-December 5, 2003.

4. H. C. Huang and O.Voskoboynikov, “Spin-dependent Hall effect in semiconductor quantum well and two-dimensional electron polirazer”, Sixth International Conference on New Phenomena in Mesoscopic Structures and Fourth International Conference on Surfaces and Interfaces of Mesoscopic Devices, Maui, Hawaii, U.S.A., November 30-December 5, 2003.

5. O.Voskoboynikov, C.M.J. Wijers, J.L. Liu, and C. P. Lee, “Magneto-optical response by a layer of semiconductor nano-rings”, Proceedings of the 20th General Conference of the Condensed Matter Division of the European Physical Society, Prague (The Czech Republic), July 19-23, 2004.

6. O. Voskoboynikov, G. Dykonov, C. M. J. Wijers, “Left handed composite materials in optical range”, Book of Abstracts, The Fifth International Conference on Low Dimensional Structures and Devices, Cancun (Mexico), December 12-17,2004.

7. O. Bauzha, O.Voskoboynikov, O. Tretyak, C. P. Lee, “Spin orbit interaction impact on magnetization of quantum dots” II Ukranian Scientific Conference on Semiconductor Physics, Chernovtsy (Ukraine), September 20-24, 2004.

8. List of thesis’s of graduated students

1. Hua-Chiang Huang, “Electron Spin-Dependent Transport in Semiconductor Heterostructures”, M.S. thesis, NCTU, Hsinchu, May 2003.

2. Leo Yu, “Electron Spin Filtering in All-Semiconductor Tunneling Structures”, M.S. thesis, NCTU, Hsinchu, June 2004.

3. Chi-Huei Chen, “Spin Orbit Splitting of Energy Levels in Semiconductor Asymmetric Double Well Structure”, M.S. thesis, NCTU, Hsinchu, June 2005.