自支撑衬底n-GaN肖特基接触的电流输运机制研究

Study on the Current Transport Mechanisms of Ni/Au/n-GaN Schottky Diodes on Free-standing Substrate

在自支撑衬底n-GaN外延片上制备了圆形Ni/Au/n-GaN肖特基接触结构,测量和分析器件的变温电流-电压(I-V)特性,研究了其正向和反向电流的输运机制。结果表明:在正向偏压下,随着温度从300K增加至420K,器件的理想因子由1.8减小至1.2,表明在高温下复合机制逐渐被热发射机制替代;在反向小偏压下,漏电流表现显著的温度和电压依赖特性,且ln(I)-E^(1/2)数据满足较好线性规律,这表明肖特基效应的电子热发射机制应占主导;而在更高的反向偏压下,电流逐渐变成温度的弱函数,且数据遵循ln(I/E^2)-1/E线性依赖关系,该行为与Fowler-Nordheim隧穿特性一致。

Circular Ni/Au/n-GaN Schottky diodes were fabricated on free-standing bulk substrate n-GaN epitaxial wafer,and the forward and reverse current transport mechanisms of the devices were studied based on the temperature-dependent current-voltage measurements.The results show that,at forward bias as the temperature increases from 300 to 420K,the ideal factor of the diodes decrease from 1.8 to 1.2,suggesting that the recombination mechanism is gradually taken over by the thermal emission mechanism at elevated temperatures;At low reverse bias,there is a strong temperature and bias dependence of the current,and the derived ln（I/E）-E^（1/2） data points show a good linear correlation,indicating the dominating role of the thermal emission process of electrons in Schottky junction;while at higher bias,the current shows a weak temperature dependence,and the ln（I/E^2）-1/E data points obey nicely linear correlation,which is in good agreement with the behaviors of the Fowler-Nordheim tunneling.