GaN发光二极管的负电容现象

采用串联等效电路分析了较大正向电压下半导体二极管的交流电学特性．由此可以同时测量结电容和串联电阻，并能判断二极管是否有界面层。首次发现了在较低的测试频率和较大的正向电压下，GaN二极管的结电容具有负值，并且测试频率越低，正向偏压越大，负电容现象越显著。这种负电容效应可能与大正向电压下强注入造成的电子-空穴复合发光有关。

Negative Capacitance Effect of GaN LEDs

A new method based on the series equivalent circuit of a diode was introduced to characterize the semiconductor diodes, through which the electrical characteristics such as the series resistance, the junction capacitance at forward bias, and the interfacial layer resistance and capacitance can be evaluated. By using this method, the p n junction blue light emitting diodes (LEDs) fabricated by the wide gap GaN semiconductor material were measured and analyzed, and the negative capacitance effect (NCE) of the GaN p n junction diodes was observed and reported firstly. The negative capacitance appears more noticeable with the lower frequencies and the larger forward bias. It is found that the negative capacitance effect is constantly accompanied by the diode lighting. This phenomenon is explained by considering the electron hole recombination lighting under high injection with large forward bias. The research on negative capacitance will be valuable for the improvement of the design, fabrication and characterization of the GaN semiconductor LEDs.