BREAKDOWN MECHANISMS IN PSEUDOMORPHIC INALAS INXGA1-XAS HIGH-ELECTRON-MOBILITY TRANSISTORS ON INP .2. ON-STATE/

A systematic experimental study on the mechanisms inducing device brea kdown in the on-state in L(G) = 0.28 mu m gate-length pseudomorphic In AlAs/InxGa1-xAs (0.53 < x < 0.7) high electron mobility transistors (H EMTs) on InP substrate is presented. The study provides comprehensive physical explanation for the mechanisms which limit the breakdown volt age in the open channel condition. The intention of this paper is to p rovide a profound understanding on the breakdown physics in the on-sta te of this type of device. From temperature dependent measurements and the evolution of the impact ionization rate as a function of bias we found that in this type of device on-state breakdown is dominated by i mpact ionization. Thermionic held emission was recognized to be neglig ible compared to impact ionization. The on-state breakdown voltage dro ps drastically with increased InAs-mole fraction x. The experimental r esults also indicate that on-state breakdown occurs in the channel lay er. The drain-source breakdown voltages determined at 1% I-DSS where V -DSbr, (300 K) = 6.8 V, 5.7 V, 4.5 V, 4.1 V, 3.5 V for x = 0.53, 0.59, 0.62, 0.65 and x = 0.7, respectively.