基于电容和电导特性分析GaN蓝光发光二极管老化机理

采用正向交流小信号方法测试和分析老化前后GaN发光二极管（LED）的电容-电压特性，结合串联电阻、理想因子、隧穿电流参数讨论负电容以及电导变化情况.基于L-V曲线定性分析老化前后负电容的阈值电压，老化之后样管的受主浓度降低，辐射复合概率下降，大量缺陷以及非辐射复合中心出现，对载流子俘获作用增强，造成负电容降低.反向偏压以及小正向偏压下，隧穿效应导致老化之后样管的电导增大；正向偏压大于2.2 V区域，考虑串联电阻效应，老化后样管电导减小.在分析LED电容-电压、光输出、电学特性曲线与老化机理基础上，通过实验论证以及理论解释表明，负电容以及电导特性可作为分析LED老化特性的参考依据. 关键词： GaN发光二极管 负电容 电导 老化机理

Analysis of degradation mechanism of GaN blue light emitting diode by the characteristics of capacitance and conductance

A study of the capacitance-voltage characteristics of GaN light emitting diode（LED） with a view to reveal its degradation mechanism is presented in this article by forward alternating current small-signal method. Combined with series resistance， ideality factor and tunneling current measurement， the properties of negative capacitance and conductance are discussed. The threshold voltage of negative capacitance during degradation is qualitatively analysed. The decreased negative capacitance during aging may be due to the decrease in the effective acceptor concentration and radiative recombination rate， and the increase of defects and non-radiative recombination centers resulting in the enhanced capture effect of carriers. The tunneling effect leads to the obvious increase of conductance under reversed and low-forward bias voltage. The decreased conductance during aging may be due to the series resistance. On the basis of the capacitance-voltage characteristic， light output， current-voltage curves with the degradation mechanism of LED， the characteristics of negative capacitance and conductance can be used as important evidence for the degradation analysis of LED as proved by experiment and theory.