发光二极管的反偏电容和电导特性研究

发光二极管(LED)在反向偏压工作状态下的电学特性在一定程度上反映PN结中载流子的传输特性。本文对反偏状态下LED的电容电导特性进行了研究,通过在直流偏置上叠加交流小信号,得到了LED反偏电容和电导随频率变化的关系。实验结果表明,随着频率的增加,LED反偏电容减小,反偏电导增加。不同I-V特性的LED具有明显不同的反偏电容电导特性。分析认为,PN结的隧穿电流和表面漏电流是引起以上现象的主因;反偏电容和电导特性可作为对LED评价的重要参数指标,实现产品质量筛选。

Reverse-biased capacitance and conductance characteristics for lighting e mitting diodes

The electrical characteristics of light emitting diode (LED) in the re verse-biased state are very important,which can reflect the transport properties of carr iers in the PN junction.In this paper,the capacitance and conductance characteristics of LED samples in the reverse-biased state are studied in experiment and theory.The capacitance and conductance as a function of modulation frequency are obtained experimentally by adding a small alternating current (AC) signal on a direct current (DC) bias voltage.Experimental results show that the capacitance decreases and the conductance increases with the increasing modulati on frequency for reverse-biased LED samples.For LEDs with different I-V characteristics,the reverse-biased capacitance and conductance characteristics are different obviously,even for th e samples with similar I-V characteristics in the forward-biased stat e.This means that the p arameters in the reverse-biased state for LED samples are associated with their properties in th e forward-biased state when working in the normal conditions.Analysis suggests that the reverse -biased capacitance and conductance characteristics mainly result from the tunneling cur rent and surface leakage current.Thus,the reverse-biased capacitance and conductance character istics can be useful parameters to evaluate the performance of light em itting diodes.