摻入銻量子點經由 PL 與 AFM 的分析，量子點分為兩群，得到銻元素有相分離的 現象，此現象導致 InSb-rich 量子點較晚出現，而後量子點隨著磊晶厚度增加而 增加。由磊晶結果得知，形成量子點的臨界厚度由 1.68ML(19.9sec)後推約至 2.0ML(24sec)，表示二維轉三維的臨界厚度增加，Sb 延緩量子點形成，此即 Sb 的表面活化效應。由低溫半高寬判定，2.8ML 的 uniformity 最好，其他較差。由 變溫 PL 與半高寬知，低溫載子有穿隧現象，高溫載子容易由 InAs-rich 量子點 跳到 InSb-rich 量子點，隨著磊晶厚度增加，密度與尺寸變大，此現象於更低溫 發生。
無摻氮樣品溫度 18K時載子時間常數仍小於 10-6秒，沒有缺陷。有摻氮樣品於溫 度 300K載子時間常數約 10--3~10-5秒，有缺陷能階產生，造成載子空乏。以深層能 階暫態頻譜與電容暫態頻譜量測，此缺陷能階位於傳導帶下方約 0.2~0.25eV，隨 著偏壓加大能階愈深，為能階分佈很廣的缺陷，缺陷濃度約 1~2.8×1015cm-3。此缺 陷的暫態電容為可以填充達到飽和的指數函數，推測應該是摻入氮引起的點缺 陷。DLTS改變填充偏壓時間與不同速率視窗，求得捕捉位能障高度 0.15eV，再配 合縱深分佈的空乏區寬度 0.25μm，要造成此空乏所需要的的缺陷濃度為
1.06×1015cm-3。因此電性量測結果有很高的一致性，將其作成缺陷的能帶模擬圖，
如圖 4.10，推測直接將氮摻入量子點會於量子點位置產生缺陷造成載子空乏，使 得原本無摻氮量子點非常短的時間常數變長為 10-3~10-5秒(室溫)。因此我們相信 可以藉由摻入氮元素於量子點來調變所需要的時間常數。
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GaAs GaAs
圖2.1 摻入銻(Sb)量子點系列樣品的能帶與結構圖 InAs QDs doped with Sb
(24s、26s、32.9s) (2.0ML、2.2ML、2.8ML) 0.256Å/sec，485ºC
n-GaAs, 0.3μm, 595ºC Si：3×1016cm-3, 3.03Å/s
n+-GaAs Substrate n-GaAs 0.3μm, 595ºC Si：3×1016cm-3 , 3.03Å/s
在同樣長晶條件下
InAs QDs without Sb InAs QDs doped with Sb
19.9s形成量子點，約1.68ML 24s形成量子點，約2.0ML
量子點形成判定是藉由反射式高能電子束繞射(Reflection High-Energy Electron Diffraction, RHEED)圖形
GaAs
圖2.2 摻入氮(N)量子點與其對照樣品的能帶與結構圖 Al
0.3µm GaAs Nd=8×1016cm-3
GaAs
In
0.14GaAs
0.3µm GaAs
InAs ( QDs )
InAsN
17%( QDs )
Nd=8×1016cm-3
n+-GaAs substrate
In Si
圖2.3 PL量測系統之架構圖
圖2.4 InAsSb ternary alloys X-ray分成InAs-rich與InSb-rich兩群 Ref. Journal of Crystal Growth vol.237–239, p1519–1524, 2002
Laser 532nm
1.3W VNDF
Chopper Focus lens
PC
Vacuum and cooling system
Long-pass filter Ref. Signal
Lock-in Amplifier
Monochromator InGaAs
GPIB Interface
Multi-meter
photodetector
(a)
(b)
(c)
防震系統
圖2.5 (a)AFM懸臂樑及針頭TEM圖(圖片來源Ultrasharp公司網站) (b)凡得瓦力與距離的關係圖
(c)AFM示意圖
(a)
1000 1100 1200 1300 1400 1500 0.0
2.0x10-3 4.0x10-3 6.0x10-3 8.0x10-3
300K 50K dots-in-well 2.7ML 10mW
int ens ity (a. u.)
wavelength(nm)
(b)
1000 1100 1200 1300 1400 1500 0.0
1.0x10-2 2.0x10-2 3.0x10-2 4.0x10-2
1mW 100mW dots-in-well 2.7ML 300K
In tensit y(a. u. )
Wavelength(nm)
圖3.1 一般dots-in-well量子點 (a) 變溫PL圖 (b)室溫300K變功率PL圖
1000 1100 1200 1300 1400 1500
Inte nsi ty( a.u .)
Wavelength(nm)
dots-in-well 2.7ML 300K
1mW 100mW
圖3.2 一般dots-in-well量子點 室溫300K變功率正規化調整PL圖
InAs-rich InSb-rich
0.52eV
0.734eV 1.424eV 0.83eV
0.24eV
量子點尺寸 量子點尺寸
圖 3.3 二群量子點室溫能階模擬圖
900 1000 1100 1200 1300 1400
dots+Sb 2.0ML 25K
Intensity(A.U.)
900 1000 1100 1200 1300 1400 0.0
6.0x10-2
dots+Sb 2.2ML 25K
intensity (a.u.)
900 1000 1100 1200 1300 1400 0.0
dots+Sb 2.8ML 25K
Wavelength(nm) (a1)2.0ML (b1)2.2ML (c1)2.8ML
900 1000 1100 1200 1300 1400
Intensity(A.U.)
Wavelength(nm)
dots+Sb 2ML 25K
15mW
900 1000 1100 1200 1300 1400
dots+Sb 2.2ML 25K
Intensity (A.U.)
900 1000 1100 1200 1300 1400
dots+Sb 2.8ML 25K
Intensity(A.U.) (a2)2.0ML (b2)2.2ML (c2)2.8ML
900 1000 1100 1200 1300 1400 0.000
0.002 0.004 0.006
dots+Sb 2.0ML 300K
Wavelength(nm)
900 1000 1100 1200 1300 1400 0.0000
0.0005 0.0010 0.0015 0.0020
dots+Sb 2.2ML 300K
intensity (a.u.)
900 1000 1100 1200 1300 1400 0.0000
0.0005 0.0010 0.0015
dots+Sb 2.8ML 300K
Intensity(A.U.) (a1)2.0ML (b1)2.2ML (c1)2.8ML
900 1000 1100 1200 1300 1400
Intensity(A.U.)
Wavelength(nm)
dots+Sb 2ML 300K
7.5mW 750mW
(a2)
900 1000 1100 1200 1300 1400
10mW 90mW
dots+Sb 2.2ML 300K
Wavelength(nm)
Intensity (A.U.)
900 1000 1100 1200 1300 1400
32mW 320mW
dots+Sb 2.8ML 300K
Intensity(A.U.)
Wavelength(nm)
(b2)
(c2)
圖3.5 室溫300K變功率正規化調整PL圖 (a2)2.0ML (b2)2.2ML (c2)2.8ML
間距小
( 密 度 大 ) 間距大
( 密
度 小 )
圖3.6 載子侷限空間分佈耦合機率圖
900 1000 1100 1200 1300 1400
900 1000 1100 1200 1300 1400 0.0
5.0x10-3 1.0x10-2 1.5x10-2 2.0x10-2
2.5x10-2
dots+Sb 2.2ML
intensity (a.u.)
900 1000 1100 1200 1300 1400 0.0
dots+Sb 2.8ML
Intensity(A.U.)
(a1)2.0ML (b1)2.2ML (c1)2.8ML
800 900 1000 1100 1200 1300 1400 1500 1600
dots+Sb 2.0ML
Intensity(A.U.)
Wavelength(nm)
25K 70K 115K 150K 180K 200K 250K 275K 300K
(a2)
900 1000 1100 1200 1300 1400 300K
25K 200K
Intensity (A.U.)
Wavelength(nm)
dots+Sb 2.2ML
(b2)
圖3.7 變溫正規化調整PL圖 (a2)2.0ML (b2)2.2ML
950 1000 1050 1100 1150 1200 1250 1300 1350 1400
dots+Sb 2.8ML
Intensity(A.U.)
Wavelength(nm)
150K 120K 80K 60K 40K 25K
(c2)
950 1000 1050 1100 1150 1200 1250 1300 1350 1400
dots+Sb 2.8ML
Intensity(A.U.)
Wavelength(nm)
210K 190K 180K 170K 160K 150K
(c3)
圖3.7 變溫正規化調整PL圖 2.8ML (c2)低溫區(c3)高溫區
0 50 100 150 200 250 300 0.06
0.08 0.10 0.12 0.14
FWHM(eV)
T(K) InAs-rich
ML2.0 ML2.2 ML2.8
0 50 100 150 200 250 300
0.03 0.04 0.05 0.06 0.07
InSb-rich
FWHM(eV)
T(K)
ML2.0 ML2.2 ML2.8
圖3.8 各樣品半高寬隨溫度變化圖 (a)InAs-rich量子點
(b)InSb-rich量子點
(a)
(b)
(c)
圖3.9 AFM平面圖
(a)2.0ML (b)2.2ML (c)2.8ML
(a)
2.0ML
(b)
2.2ML
(c)
2.8ML
圖3.10 AFM 3D圖
(a)2.0ML (b)2.2ML (c)2.8ML
102 103 104 105 106 107 108
InAsN/InGaAs 300K
C(pF)
InAsN/InGaAs 300K
-2V -1.5V
1000 10000 1000001000000 1E7 1E8 0
50 100 150
InAsN/InGaAs -1.5volt
G/f(pS/Hz) ln( τ T
2) (sec-K
2)
-1.5V Ea=0.34eV σ=4.16E-16 cm2
-0.5V Ea=0.08eV σ=2.63E-19 cm2 -1V Ea=0.13eV σ=1.13E-18 cm2 -2V Ea=0.38eV σ=5.74E-16 cm2 -2.5V Ea=0.41eV σ=3.10E-16 cm2
圖4.2 (a)變溫G/f-f量測偏壓1.5v (b)各偏壓的Arrhenius plot
(a)
150 200 250 300
-1.0
v=-1~-1.5volt
τ=0.86ms
∆ C(pF)
T(K)
filling pulse tp 0.05ms
150 200 250 300
-1.0
v=-1~-1.5volt
τ=2.15ms
∆ C(pF )
T(K)
filling pulse tp 0.05ms
50 100 150 200 250 300
filling pulse tp 0.05ms
v=-1~-1.5volt
τ=4.3ms
(c)v=-1~-1.5volt
τ=8.6ms
∆ C(pF)
T(K)
filling pulse tp 0.05ms
-1 0 1 2 3 4 5 6 7 8 -4.0
-3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0
ln(1-S(t
p)/S( ))
t
p(ms)
τ=8.6ms C=0.824 s-1 T=205K τ=4.3ms C=1.468 s-1 T=215K τ=2.15ms C=2.067 s-1 T=228K τ=0.86ms C=3.243 s-1 T=242.5K
(a)
4.0 4.2 4.4 4.6 4.8 5.0
-57.0 -56.5 -56.0 -55.5 -55.0
ln( σ ) (cm
2)
1000/T(1/K)
E
σ=0.151eV
(b)圖4.4 (a)不同速率視窗之對應溫度及其捕捉速率 (b)捕捉位能障
(a) (a) -1~-1.5v Emission
(b) -1.5~-1v Capture
(a)
ln( τ T
2) (sec-K
2)
1000/T(1/K)
ln( τ T
2) (se c -K
2)
1000/T(1/K)
圖4.6 暫態電容(Transient)量測所得Arrhenius plot (a) -1~-1.5v Emission
(b) -1.5~-1v Capture
(b) (a) -1.5~-2v Emission
(b) -2~-1.5v Capture
0 50 100 150 200 0.01
0.1 1
Emission
δ
C(t)/
δC(0)
Time(sec)
120K 125K 130K 135K 140K
(a)
0 10 20 30 40 50
0.01 0.1 1
Capture
δ C(t )/ δ C(0)
Time(sec)
120K 125K (b)
圖4.8 △C(t)/△C(0) (a)Emission (b)Capture
7.0 7.5 8.0 8.5 10
11 12 13
14
Emission
ln( τ T
2) (sec-K
2)
1000/T(1/K)
Ea=0.25 eV σ =2.5E-16 cm2
(a)
8.0 8.2 8.4
11.0 11.5 12.0
Ea=0.19eV σ =3.4E-18 cm2
Capture
ln (
τT
2)(sec-K
2)
1000/T (1/K)
(b)圖4.9 暫態電容(Transient)量測所得Arrhenius plot (a) -1.5~-2v Emission (b) -2 ~-1.5v Capture
圖4.10 缺陷能帶模擬圖