2D photonic crystal membrane with a point defect inhibiting light propagation in horizontal direction could be used as resonant micro-cavity, which leads to small mode volume and high quality factor value merits. Type II GaAsSb/GaAs quantum well structure is profitable to 1.3 μ m emission wavelength with less attenuation characteristic.
In this thesis, type II GaAsSb/GaAs tri-quantum well layers with photonic crystal structure are successfully fabricated by molecular beam epitaxy, e-beam lithography and relative ion etching (RIE) technology. The total process flow is introduced in detail in chapter 3.2. We design ‘wet etching window’ at both sides of photonic crystal pattern to make wet etching process more smoothly and SEM observation more conveniently. In addition, the experimental condition of measurement system is described. Co-focal microscope and 100 magnification object lens are used so as to concentrate beam spot on micro-cavity region which is only 3-4 μm2. Also empirical temperature is 77K by liquid nitrogen cooling system since surface velocity, dominated mechanism of non-radiative recombination, of GaAs is 2*107 cm2. To design appropriate photonic crystal pattern, ‘Plane Wave Expansion method’ is used to decide band gap range and cavity mode at the middle of band gap. In 2D simulation, instead of time-consuming 3D simulation, bulk refractive index must be replaced by effective refractive index because of the affection of surrounding air layer. Next various micro-cavity structures are designed:
neighboring six holes of defect are shrunk and shifted at the same time to make six holes radius, r’, plus shift distance, d, equal to other hole radius, r. The aim
to this design is that vertical quality factor, main mechanism of total quality factor, increases by changing neighboring six holes shapes and positions.
Besides, according to variational principle, central wavelength of cavity mode will incline to shorter wavelength when air hole portions increases in order to maintain the lowest energy, we demonstrate this principle with our simulations, for instance, change hole radius, r, for a constant lattice constant. In 3D simulation, each quality factor values of various micro-cavity patterns are calculated and the quality factor value of neighboring six holes radius, r’=0.8r, is the highest. Finally cavity mode of our pattern was measured. The emission range of our type II GaAsSb/GaAs quantum well is from 950nm to 1050nm. In terms of simulation, only one cavity mode is located within the emission range, same as the measurement. The highest two quality factors of different cavity structures were measured. For cavity with r’=0.7r, the central wavelength of cavity mode was 1003.08 nm and Δλ(half max)was 0.08 nm by Lorentz fitting.
That is, the quality factor of this cavity mode, up to 15000, was achieved. To our knowledge, this is the first time that a type-II heterstructure emission was coupled to a photonic nanocavity with a very sharp emission and a high Q value. Besides, the quality factor of cavity with r’=0.8r was higher than that of cavity with r’=0.7r since Δλ(half max) of cavity with r’=0.8r was narrower than cavity with r’=0.7r, corresponding to our simulation. Moreover, central wavelength of cavity with r’=0.8r was shorter than r’=0.7r, which is satisfied with variational principle. Basis on our experimental results, it is promising for 1.3μm laser source.
In order to develop 1.3μm laser, in the experiment, exciting another cavity mode with higher quality factor value, like quadrapole or hexapole, is
necessary for low threshold current. Besides, the value of x of GaAsxSb1-x/GaAs is needed to make some adjustment to accomplish 1.3μm emission. In measurement system, pulse laser source with high power is needed since thermal effect is serious due to surrounding air layer which thermal conduction coefficient is very low. Besides, TRPL can measure life time of excited photon and polarizer measurement can ensure which kind of pole of cavity mode is excited. Finally, it’s hopeful to realize laser source by electric pumping.
Reference
[1]Andrew S. Tanenbaum, “Computer Networks”, Upper Saddle River, N.J.
Prentice Hall PTR, 1996
[2]V. Swaminathan, “Material Aspects of GaAs and InP Based Structures”, Prentice-Hall, Inc., 1991
[3] E. Yablonovitch, “Inhibited Spontaneous Emission in Solid-State Physics and Electronics”, Phys. Rev. Lett. 58, 2059, 1987.
[4] S. John, “Strong localization of photons in certain disordered dielectric superlattices”, Phys. Rev. Lett. 58, 2486, 1987.
[5] O. Painter et al., “Two-dimensional photonic band-gap defect mode Laser,”
Science 284, 1819, 1999
[6] Yoshihiro Akahane et al., “High-Q photonic nanocavity in a two-dimensional photonic crystal” Nature 425, 944, 2003
[7] K. Noazki et al. “Laser characteristics with ultimate-small modal volume in photonic crystal salb point-shift nanolasers”, Appl. Phys. Lett, 88, 211101, 2006 [8] T. Anan et al, “GaAsSb: A novel material for 1.3μm VCSELs,” Electronics Lett.
34, 2127, 1998
[9]O. Blum and J. F. Klem, “Characteristics of GaAsSb single-quantum-well-lasers emitting near 1.3μm,” IEEE Photonics Tech. Lett.12, 771,2000
[10] S. W. Ryu and P. D. Dapkus, “Low threshold current density GaAsSbquantum well lasers grown by metal organic chemical vapor deposition on GaAs substrates,”
Electronics Lett. 36, 1387,2000
[11] P.-W. Liu, G.-H. Liao and H.-H. Lin, “1.3 lm GaAs=GaAsSb quantum well laser grown by solid source molecular beam epitaxy”, Electronics Lett. 40, 177, 2004 [12] T.Anan et al, “Room-temperature pulsed operation of GaAsSb/GaAs
vertical-cavity surface emitting lasers”, Electronics Lett. 35, 903, 2001
[13] F. Quochi et al, “Continuous-Wave Operation of a 1.3-μm GaAsSb–GaAs Quantum-well vertical-cavity surface-emitting Laser at room temperature”, IEEE Photonic Tech Lett. 13, 921, 2001
[14] T.Baier et al, “Type-II band alignment in Si/Si1-xGex quantum wells from photoluminescence line shifts due to optically induced band-bending effects:
Experiment and theory”, Physics Review B 50, 15190, 1994
[15] W.W. Chow, H.C. Schneider, “Charge-separation effects in 1.3 mm GaAsSb type-II quantum-well laser gain”, Appl. Phys. Lett. 78, 4100, 2001
[16] D.S. Jiang et al., “Structural and optical properties of GaAsSb/GaAs heterostructure quantum wells”, Journal of Crystal Growth 268, 336, 2004
[17] Y. S. Chiu et al “Properties of photoluminescence in type-II GaAsSb/GaAs multiple quantum wells”, Journal of Applied Physics 92, 5810, 2002
[18]John. D. Joannopoulos, Robert D. Meade, and Joshua N. Winn, Photonic crystals:
molding the flow of light, 2nd, New Jersey, 2008
[19] Fujita, M. et al., “Simultaneous inhibition and redistribution of spontaneous light emission in photonic crystals”, Science 308, 1296, 2005
[20]K. Kounoike et al., “Investigation of spontaneous emission from quantum dots embedded in two-dimensional photonic-crystal slab”, Electronics Letters 41, 1402, 2005
[21] Hong-Gyu Park et al., “Characteristics of Modified Single-Defect
Two-Dimensional Photonic Crystal Lasers”, IEEE Journal of Quantum Eelctronics 38, 1353, 2002
[22] N. Carlesson et al., “Design, nano-fabrication and analysis of near-infrared 2D photonic crystal air-bridge structures”, Optical and Quantum Electronics 34, 123,
[23] Jong-Hee Kim, Dae Ho Lim, and Gye Mo Yang, “Selective etching of AlGaAs/GaAs structures using the solutions of citric acid/H2O2 and de-ionized H2O/buffered oxide etch”, J. Vac. Sci. Technol. B 16, 558, ,1998”
[24] K. Sakoda, Optic Properties of Photonic Crystals, Springer, 2001
[25] D. G. Gevaux et al., “Enhancement and suppression of spontaneous emission by temperature tuning InAs quantum dots to photonic crystal cavities”, Appl. Phys, Lett.
88, 131101, 2006
[26] K.S. Yee, ‘Numerical solution of initial boundary value problems involving maxwell’s equations in isotropic media,’ IEEE Trans. Antennas Propag. , 14, 302, 1966
Autobiography(自傳)
姓名:林俊豪(Lin,Chun-Hao) 性別:男
出生年月日:民國 74 年 8 月 24 日 學歷:
國立交通大學電子工程學系(92.9-96.6)
國立交通大學電子工程研究所碩士班(96.9-98.10) 碩士論文題目:
利用光激發於結合光子晶體的類型二量子井之研究
Study of Type II QW with photonic crystal structure by optical Pumping