銻化物高電子遷移率電晶體研究

Abstract

這篇論文主要是研究銻(Sb)化物材料的高電子遷移率電晶體元件(HEMT)的 開發。由於銻化物材料和砷化鎵(GaAs)基板之間的晶格差異很大，所以在使用分 子束磊晶系統(MBE)的過程需要透過變晶成長的方式進行磊晶。藉由實驗我們成 功成長出高電子遷移率的試片(22700cm2V-1s-1)。此外，對於閘極長度為2um 的 電晶體，傳導率(transconductance)為730mS/mm。對於閘極長度為50nm 的電晶 體，其截止頻率(ft)和最大震盪頻率(fmax)分別為50GHz 和5GHz。 除此之外，由於銻化物材料本身的能帶間隙非常的小，因此元件在操作的過 程很容易就產生碰撞游離，造成糾結效應(Kink effect)。本研究也展示了透過主動區的結構調整，可以加大能帶間隙，進而提高糾結效應所造成的軟性崩潰電壓(soft-breakdown voltage)。

This thesis focuses on the development of Sb-based High Electron Mobility Transistor (HEMT). In this work, because of the large lattice mismatch, the Sb-based HEMT is grown on semi-insulating GaAs substrate by using metamorphic MBE growth. The best electron mobility we obtained is 22700cm2V-1s-1 by experiments. In addition, the fabricated device showed the maximum transconductance is 730mS/mm at a high drain bias Vd=1.6V for a 2um gate length device. The cut-off frequency (ft) is 50GHz and the maximum oscillation frequency (fmax) is 5GHz for a 50nm gate length device. Furthermore, due to the narrow band gap of Sb-based material, the device would generate impact ionization easily and cause the kink effect. This work also demonstrates the adjustment of the channel structure to enlarge the soft-breakdown voltage resulting from kink effect.