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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2.2V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.
The capacitance-voltage characteristics of GaN LED before and after aging were tested and analyzed by using the forward AC small signal method. The negative capacitance and the conductance change were discussed based on the series resistance, ideal factor and tunneling current parameters. Based on the LV curve, The threshold voltage of negative capacitance, the decrease of the acceptor concentration of the sample tube after aging, the decrease of the recombination rate of radiation, the large number of defects and the emergence of non-radiative recombination centers enhance the carrier trapping and reduce the negative capacitance. Under the bias voltage, the tunneling effect leads to the increase of the conductance of the sample tube after aging. When the forward bias voltage is larger than 2.2V, the conductance of the series resistor is reduced considering the series resistance effect. Electrical characteristics and aging mechanism, based on experimental proofs and theoretical explanations show that negative capacitance and conductance characteristics can be used as a reference to analyze LED aging characteristics.