GaSb基晶格失配GaInSb薄膜的生长及其应用于热光伏电池的基础研究

Thermophotovoltaic(TPV) systems convert heat into electricity directly,which have the advantages of high output power densities,non pollution and noise etc.Recently, narrow bandgap antimonide-based TPV cell for low temperature(≤1000℃) radiation conversion have received extensive attention because of their high stability and safety coefficient characteristics.The optimum bandgap(Eg) of TPV cell that applied in low temperature should be lower then 0.5eV, and GaInSb can get this Eg by adjusting compositions.This project proposed a lattice-mismatched GaInSb(Eg≤0.5eV)/GaSb thin film TPV cell.The GaInSb thin film will be fabricated on GaSb substrate by LP-MOCVD, and a graded buffer layer is incorporated to accommodate the lattice mismatch between the epitaxial layer and substrate.The effect of crystal lattice "overshoot" on the residual strain near the surface of graded buffer layer will be studed.The structure and growth parameters will be optimized to reduce the densities of threading dislocations.The GaInSb active layer will be grew on buffer layer,and GaInSb TPV device simple will be fabricated and tested.Based on the theoretical simulation and experimental data of the practical material and device,the characteristics of threading dislocations and GaInSb/buffer interface state will be studied to reveal their impact mechanisms on the performances of TPV cell,and the way to reduce this impact will be studied in detail.Based on the strong self-absorption effects of GaInSb,the back surface reflector is adopted to let the photons double pass the active p-n junction,and the structure will be optimized.This project has important theoretical and application significance for developing high efficiency nerrow bandgap TPV cell for low temperature heat source energy conversion.

用于低温辐射体(≤1000℃)能量转换的锑化物热光伏(TPV)电池技术是一种高输出电功率密度、高稳定性、安全可靠的热电直接能量转换技术，成为一个研究热点。用于此的电池最佳禁带宽度(Eg)在0.5eV以下。本项目用低压MOCVD法生长GaSb基晶格失配GaInSb(Eg≤0.5eV)薄膜。引入GaInSb组份渐变缓冲层降低外延层和衬底之间的失配应力。研究晶格"过冲"对渐变层表面残留应变的影响，优化结构和工艺以降低穿透位错密度。在缓冲层上生长GaInSb有源层，制备TPV器件并测试其性能。通过对实验测试和理论分析相结合，研究失配导致的穿透位错和GaInSb/缓冲层界面态对器件性能的影响，揭示其物理机理，探索降低其影响的途径。利用GaInSb的载流子自吸收特性为器件引入背反电极，理论上实现以光厚电薄为目标的结构优化。项目对推动高效低成本低温辐射体TPV技术的发展具有重要的理论意义和实际应用价值。

应用于低温辐射体能量转换的窄禁带热光伏（TPV）电池具有较高的稳定性和安全性，可应用于环保节能汽车、工业废热发电等场合，成为当今的研究热点。三元合金GaInSb通过调节组分能获得较低Eg值(0.17-0.72eV)，但是其晶格常数和Eg一一对应，没有晶格匹配的衬底。本项目用低压金属有机化学气相沉积方法(LPMOCVD)生长GaSb 基GaInSb 薄膜，对其TPV 电池的工艺和理论进行研究。研究内容为：1) 采用LPMOCVD方法进行GaInSb/GaSb薄膜生长实验，最佳生长参数T=480℃、P=150mbar、V/III为0.75，表面光滑平整，薄膜取向与衬底一致。设计GaInSb渐变式缓冲层结构，采用HRXRD方法研究其生长工艺，在540℃生长温度下实现缓冲层晶格弛豫度95%，残余应变0.06%，材料禁带宽度0.55eV，满足TPV电池应用要求；2) 制备了GaInSb/GaSb热光伏电池，外量子效率在1.5µm波长45%，短路电流密度1.58A/cm2，电压因子0.47，填充因子48%，输出电功率密度0.198W/cm2；3) 设计、模拟并优化了GaSb/GaInSb热光伏电池。理论结果表明，辐射体温度为1200K时，单结电池最佳有源层材料结构为0.2–0.5μm厚的N型基区和4.5–6μm厚的P型发射区，最佳掺杂浓度1-3e17cm-3，低能光子的回收率从0%增加到90%时，电池效率从7% 增加到22%。理论结果表明双结GaSb/GaInSb电池的开路电压0.95V，短路电流15.1209A/cm2，填充因子77.8317%，效率17.31%；4）制备了PMMA微球，进而以此作为模版制备光子晶体，合成了钨酸锌（ZnWO4）光子晶体和二氧化硅微球结构，验证了该种光子晶体的带隙和发射光谱可以通过改变尺寸进行调节，在TPV电池领域具有重要的应用价值。三元合金GaInSb与四元GaInAsSb相比，其材料和工艺成本更低，在低成本低温热辐射源TPV技术领域具有更广阔的应用前景，相关工作对推动低温辐射体TPV 技术在环保节能汽车、新能源开发利用、航空航天器的供电系统等领域的应用有重要的价值。