热退火对Mg掺杂InGaN/GaN异质结特性的影响

Thermal Annealing Effect on Mg-doped InGaN/GaN Heterostructures in O_2 Ambient

系统地研究了氧气氛围中退火温度对Mg掺杂InGaN/GaN异质结电学特性及光学性能的影响。电流电压特性和表面方块电阻的测试表明,与p-GaN相比,p-InGaN/GaN异质结的最佳退火温度较低,而且容易与非合金化的Ni/Au电极形成欧姆接触。分析认为InGaN具有的较小带隙能量和p-InGaN/GaN异质结中存在强烈的极化效应以及InN较高的平衡蒸汽压是引起以上结果的主要原因。p-InGaN/GaN异质结10 K的光致荧光光谱中存在两个分别位于2.95eV和2.25 eV的发光峰,随着材料退火温度的提高,这两个发光峰的强度逐渐降低。提出了类施主补偿中心参与的与H相关的络合物与Mg受主的复合发光机制,对退火前后光致荧光光谱的变化进行了解释。

The effect of the thermal annealing temperature on the electrical and optical properties of Mg-doped InGaN/GaN heterostructures in O2 ambient was systematically investigated. The currentvoltage characteristics and surface sheet resistance measurements show that, compared with p-GaN, the optimum annealing temperature of p-InGaN/GaN heterostructures is lower and the nonalloyed Ni/Au ohmic contacts can be obtained. It is suggested that relative narrower bandgap of InGaN, strong polarization effect in p-InGaN/GaN heterosturctures,and equilibrium vapor pressure of nitrogen over InN higher than that over GaN are the main reasons for the above results. Furthermore, in the photoluminescence spectrum at 10 K of the as-grown p-InGaN/GaN heterostructures,there are two peaks centered at 2. 95 eV and 2. 25 eV respectively, whose intensities gradually decrease when the thermal annealing temperature increases. To explain the photoluminescence spectra,the recombination mechanism between H-related complex and Mg-acceptor,in which donor-like compensating center play an important role, was proposed.