Structural, Electrical and Optical Properties of Defects in GaN-based Materials

最近，基于iii族氮化物的超亮蓝绿发光二极管（led）和激光二极管的突破，以及高温（- 500℃）、高场、高频电子学的前景，激发了人们对GaN、A1N、InN及其合金、量子阱（QWs）和超晶格（SL）结构的基本性质的极大科学兴趣。这些光子器件对于光纤通信系统、光计算、光互连至关重要；数据传输和信号处理。为了充分利用这些技术上重要的材料的潜力，可控的掺杂显然是必要的。尽管近年来进行了大量的实验工作，但围绕着内在缺陷的识别和表征，特别是它们与掺杂iii族氮化物的补偿机制的关联，仍然存在许多争议和谜团。已知氢和天然缺陷都在氮化镓中起重要的补偿中心作用。红外光谱可以提供关于氢的掺入和/或在n型和p型材料中与掺杂剂形成配合物的本征缺陷的信息。在III-V型半导体（如GaAs）中，傅里叶变换红外光谱（FT-IR）先前观察到的不同振动模式为建立双相（如硅，碳等）杂质和复合物（如SiGa- VGGa， BeGa,- AsGa， As-H等）缺陷中心的位点选择性提供了宝贵的信息。通过让本科生参与这个项目，我们将集中在三个主要任务上：(i)利用局部振动模式光谱识别n型和p型GaN， A1N和AlxGa1-x， n合金中天然缺陷的存在及其与杂质的相互作用。（ii）基于格林函数形式进行群论和现实模型计算，以促进FT-IR光谱研究。（iii）研究量子阱的电子特性，以及用于器件应用的量子阱。＊＊＊

9906077TalwarRecent breakthroughs in group III-nitride based super bright blue-green light emitting diodes (LEDs) and laser diodes, and the prospects of high temperature (- 500 0C), high field, high-frequency electronics, have spurred a great deal of scientific interest in the basic properties of GaN, A1N, InN, their alloys, quantum wells (QWs) and superlattice (SL) structures. These photonic devices are critically important for optical fiber communication systems, optical computing , optical interconnects; data transmission and signal processing. To exploit fully the potential of these technologically important materials, controllable doping is an obvious necessity. Despite numerous experimental efforts made in recent years, there is still much controversy and mystery surrounding the identification and characterization of intrinsic defects, especially their association with compensation mechanisms in doped group III-nitrides. Both hydrogen and native defects are known to play important role as compensating centers in GaN. Infrared spectroscopy can provide information about the incorporation of hydrogen and/or intrinsic defects forming complexes with the dopants in n- and p-type materials. In III-V semiconductors (e.g., GaAs), distinct vibrational modes observed earlier by Fourier transform infrared (FT-IR) spectroscopy provided invaluable information in establishing the site selectivity of amphoteric (e.g., silicon, carbon, etc.) impurities, and complex (e.g., SiGa- VGGa, BeGa,- AsGa, As-H etc.) defect centers. By involving undergraduate students in this project, we will focus m three major tasks: (i) Identifying the presence of native defects and their interactions with impurities in n- and p-type GaN, A1N and AlxGa1-x,N alloys using local vibrational mode spectroscopy. (ii) Performing Group theory and realistic model calculations based m Green's function formalism to facilitate the FT-IR spectroscopic investigations. (iii) Studying the electronic properties of QWs, and SLs for device applications. ***