Al2O3介质层厚度对AlGaN/GaN金属氧化物半导体-高电子迁移率晶体管性能的影响

Effect of Al_2O_3 dielectric layer thickness on the AlGaN/GaN metal-oxide-semiconductor higher-electron-mobility transistor characteristics

在蓝宝石衬底上采用原子层淀积法制作了三种不同Al2O3介质层厚度的绝缘栅高电子迁移率晶体管.通过对三种器件的栅电容、栅泄漏电流、输出和转移特性的测试表明:随着Al2O3介质层厚度的增加,器件的栅控能力逐渐减弱,但是其栅泄漏电流明显降低,击穿电压相应提高.通过分析认为薄的绝缘层能够提供大的栅电容,因此其阈值电压较小,但是绝缘性能较差,并不能很好地抑制栅电流的泄漏;其次随着介质厚度的增加,可以对栅极施加更高的正偏压,因此获得了更高的最大饱和电流.另外,对三种器件的C-V与跨导特性的深入分析证明了较厚的Al2O3层拥有更好的介质质量与钝化效果.

Three kinds of metal-oxide-semiconductor high-electron-mobility transistors（MOS-HEMTs）with different thickness of Al_2O_3 dielectric layer were fabricated on the same wafer by atomic layer deposition.The measurement results of MOS capacitance,gate leakage current,and the output and transfer characteristics indicate that the control capability of the gate on two-dimentional electron gas will be reduced,while the gate leakage current will be decreased and the breakdown voltage will be increased with the increase of the A12 03 dielectric layer thickness. Our analysis shows that the thinner the dielectric layer is, the greater the gate capacitance will be, which leads to greater negative shift of threshold voltage and much poorer insulating performance in restraining gate leakage current. Otherwise, with the increase of dielectric layer, higher gate voltage will be applied to obtain higher maximum saturation current density. Moreover, a thorough analysis of the transconductance and the capacity-voltage （ C- V） characteristic shows that better passivation effect and insulating performance can be obtained with thicker dielectric layers.