陳永芳臺灣大學：物理研究所陳宗德Chen, Tzung-TeTzung-TeChen2007-11-262018-06-282007-11-262018-06-282004http://ntur.lib.ntu.edu.tw//handle/246246/54599在本文中，我們研究銻砷化鎵/砷化鎵第二型多重量子井之光電特性研究，並藉由光激螢光光譜 (PL), 光激螢光激發光譜 (PLE), 光電導光譜 (PC), 持續性光電導光譜 (PPC) 等實驗來研究其物理性質。這些研究對於此類材料的應用有十分大的幫助。 I. 銻砷化鎵/砷化鎵第二型多重量子井之光學性質研究 我們仔細研究銻砷化鎵/砷化鎵(100)第二型多重量子井之光學躍遷。在理論的計算上，我們考慮彈性應變位能的壓縮性雙軸應力及量子侷限效應，用來比對我們的實驗。由變溫的PL實驗，我們可以看到很明顯的不對稱性，高溫時高能量邊的不對稱性是由於高能階的激發，低溫時低能量邊的不對稱性是由於量子侷Stark效應。此外低溫下變雷射光強度的PL光譜，使我們能進一步研究其不對稱性變化。而側面激發的偏振PLE藉由selection rule及理論的計算使type-I及type-II的heavy-hole及light-hole躍遷訊號得到確認。 II. 銻砷化鎵/砷化鎵多重量子井之持續性光電導 銻砷化鎵/砷化鎵(100)第二型多重量子井藉由PPC的量測，其隨著時間衰減的強度曲線，可以由一stretched-exponential函數 : Ippc(t)= Ippc(0)exp[-(t/τ)β], (0<β<1) 來描述。由變波長、變溫的PPC實驗對照PL光譜，我們推斷其PPC的產生是由於空間分離的光激電子電洞對的復合障礙所致。其成因是因為在GaAsSb的介面上有電子被defect的困住，使得電子必須越過type-II PL及GaAsSb type-I的bandgap之間的能量差，才能和電洞復合。In this thesis we report the studies of optical and electrical properties on type-II GaAs0.7Sb0.3/GaAs multiple quantum wells. Photoluminescence (PL), photoluminescence excitation (PLE), photoconductivity (PC), and persistent photoconductivity (PPC) have been performed. Some peculiar results have been obtained from our studies which very useful for the understanding as well as application of these materials. They are presented as follows. I. Optical studies of strained type-II GaAs0.7Sb0.3/GaAs multiple quantum wells We report a detailed investigation on the optical transitions of strained type-II GaAs0.7Sb0.3/GaAs (100) multiple quantum wells. For the theoretical calculations, both of the elastic deformational potential of intrinsic compressive biaxial strain, and quantum confinement effects are included. The asymmetric photoluminescence spectra reveal the features of excited state transition and quantum confinement Stark effect (QCSE) at high and low temperatures, respectively. The asymmetry features have also been investigated and confirmed by low-temperature photoluminescence experiments under different excitation power. From polarized photoluminescence excitation and photoconductivity spectra, both of the type-I and type-II optical transitions can also be clearly identified. II. Persistent photoconductivity in GaAs0.7Sb0.3/GaAs multiple quantum wells The optoelectronic properties of undoped type-II GaAs0.7Sb0.3/GaAs (100) multiple quantum wells has been investigated by photoluminescence (PL), and photoconductivity (PC) measurements. Interestingly, persistent photoconductivity (PPC) has been discovered in this novel material. The decay kinetics of the PPC effect can be well described by a stretched-exponential function Ippc(t)= Ippc(0)exp[-(t/τ)β], (0<β<1). Through the study of the PPC effect under various condition, and combining with the characteristics of the PL spectra, we identify that the origin of the PPC effect arises from the spatial separation of photoexcited electrons and holes, in which electrons fall into the GaAs layer, and holes are trapped by defects in the GaAsSb layer. In order to return to the initial states, photoexcited electrons have to overcome the energy barrier between the type-II transition and the band gap of the GaAsSb layer.List of figures …………………………………………………………..iii List of tables ………………………………………………………..…..vi 1. Introduction ……………………………………………………….…1 2. Theoretical Background and Sample preparation ……………...…6 2.1 Photoluminescence (PL) ………………………………………....6 2.1.1 Photoluminescence ………………………………………...6 2.1.2 Photoluminescence Apparatus ……………………………..8 2.2 Photoluminescence Excitation (PLE) …………………………..13 2.3 Photoconductivity (PC) …………………………...……………16 2.3.1 Photoconductivity ………………………………..……….17 2.3.2 Photoconductivity Apparatus …………………………….17 2.4 Persistent Photoconductivity (PPC) ……………………..……..21 2.5 Sample Preparation ……………………………………………..27 3. Optical studies of strained type-II GaAs0.7Sb0.3/GaAs multiple quantum wells …………………………………………………………30 3.1 Introduction …………………………………………………....30 3.2 Experiments ………………………………………………..….31 3.3 Theoretical Calculation ………………………………………..32 3.3.1 Strain effect in lattice mismatched QW ……………….…32 3.3.2 Calculation of band-structure with Strain effect …………35 3.4 Results and Discussion ………………………………………..45 3.5 Summary ………………………………………………………54 4. Persistent photoconductivity in GaAs0.7Sb0.3/GaAs multiple quantum wells …………………………………………………………56 4.1 Introduction ……………………………………………………56 4.2 Experiments ……………………………………………….…..57 4.3 Results and Discussion …………………………….………….58 4.4 Summary ………………………………………………………68 5. Conclusion …………………………………………………..………702315870 bytesapplication/pdfen-US光激螢光光譜銻砷化鎵光激螢光激發光譜pleplGaAsSbthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/54599/1/ntu-93-R90222045-1.pdf