- 學位論文
研究以氣態源分子束磊晶技術成長之砷化銦基底的材料與元件
Study on the InAs-based materials and devices grown by a molecular beam epitaxy system
摘要
InAs相關材料與元件適合於中紅外光波段的多項應用。我們研究以分子束磊晶技術所成長之InAs相關材料與元件的光學與結構特性。 我們測量InAsSb/InAs0.67P0.23Sb0.10多週量子井10到300 K的光激發螢光頻譜，從量子井的放光能量與溫度關係擬合出其能帶排列。InAsSb/InAs0.67P0.23Sb0.10為第一型量子井。我們發現富含As的InAsSb其能隙彎曲有65％來自價電帶的貢獻，我們並以價電帶反交錯模型解釋其能帶排列之行為。我們並以此模型解釋文獻中以光調製反射光譜所量得的自旋軌域分裂能與Sb含量之關係。我們並分析多週量子井其光激發螢光積分強度與溫度倒數的Arrhenius圖，研究量子井的熱焠滅機制。我們將兩個活化能分別歸因為電子電洞對脫離量子井束縛，以及電子單獨跳出量子井束縛造成。 我們以大能隙且晶格匹配的InAsPSb做為窗口層，使用分子束磊晶技術成長並製作InAsPSb/InAs的PIN光偵測器結構。光電流反應度位於波長3微米處的峰值約為1.64 A/W，外部量子效率為67%。我們以FTIR測量摻雜Be的InAsPSb層反射率，於波長3微米的反射率約為65%，顯示我們所製作的光偵測器內部量子效率相當接近100%，偵測率峰值最大可達到5.4×109 cm∙Hz1/2/W。 我們以倒置空間圖譜與X光精密吸收光譜研究成長於GaAs基板上高度不匹配磊晶層InP0.52Sb0.48與InAsPSb的晶格結構特性。其結果顯示雖然磊晶層厚度已經到達臨界厚度的200至300倍，磊晶層中仍有不小的殘留應變，其中InAsPSb的其中的垂直水平晶格常數比（az/axy）隨著As含量減少而增加，最大的az/axy可達1.017。我們以價力場模型計算樣品的畸變能，其中算得的鍵長與X光吸收光譜量得相仿，驗證模型之計算可信。價力場模型計算顯示，InAsPSb樣品內部鍵結扭曲的畸變能隨著As含量減少而增加。我們認為磊晶層之殘留應變可能是由內部鍵結扭曲所造成的加工應變引起。
並列摘要
We determined the unstrained conduction band and valence band edge energies of InAs1-xSbx (0.05 < x < 0.13) by fitting the photoluminescence (PL) peak energy of InAsSb/InAs0.67P0.23Sb0.10 multiple quantum wells (QWs) that was measured in the temperature range 10 – 300 K. The results reveal that the QWs exhibit type-I band alignment. Furthermore, the valence band accounts for 65% of the energy gap bowing of InAsSb. We propose a valence-band anticrossing (VBAC) model to explain the bowing of the valence band in InAsSb. Moreover, the spin-orbit splitting energy of InAsSb calculated by our VBAC model fits well with the experimental results reported in the previous studies. From the Arrhenius plot of the PL integrated intensity, two activation energies of each sample are retrieved. We calculated the energy of electrons escape from the conduction band confinement and the electron hole pairs escape from the QW confinement based on the InAsSb/InAs0.67P0.23Sb0.10 band alignment. One of the composition dependence of the activation energies is close to the one of the carriers escape energy. Therefore, we attributed the activation energies to the carrier bipolar emission from the QW confinement. The other activation energy could be due to the electron escape from the MQW. We used the high energy gap and lattice matched InAsPSb as the window layer and studied the InAsPSb/InAs hetero-junction PIN photodetectors. The best responsivity of a 1.5 μm i-layer sample is 1.64 A/W at the wavelength of 3.0 μm. If the 65% transmittance of the surface of the devices is considered, the internal quantum efficiency can be as high as 100%. And a peak of detectivity of 5.4x109 cm-Hz1/2/W was obtained at the wavelength of 3.0 μm. We performed reciprocal space mapping (RSM) and extended X-ray absorption fine structure (EXAFS) to investigate the lattice structure of 1-μm-thick InP0.52Sb0.48 and InAsPSb grown on GaAs substrates. The thickness of the epilayer is much larger than the critical thickness. The RSM data reveals that the average vertical to horizontal lattice constant ratio (az/axy) of the InAsPSb samples increases as the As mole fraction decreases. We used a valence force field model to calculate the distortion energy and bond lengths of InPSb and InAsPSb supercells with different az/axy ratio. The calculated bond lengths are in good agreement with the results of EXAFS. The bond lengths are close to those in corresponding end-point binaries. The distortion energy of the InAsPSb sample increases as the As mole fraction decreases. Therefore, we attributed the strain sustained in the alloys to work hardening due to the strongly distorted bonds.