AL0.25IN0.75P AL0.48IN0.52AS/GA0.35IN0.65AS GRADED CHANNEL PSEUDOMORPHIC HEMTS WITH HIGH CHANNEL-BREAKDOWN VOLTAGE/

A new Al0.25ln0.75P/Al0.48In0.52As/Ga0.35In0.65As pseudomorphic HEMT w here the InAs mole fraction of the Ga1-xInxAs channel was graded (x = 0.53 --> 0.65 --> 0.53) is described. The modification of the quantum well channel significantly improved breakdown characteristics. In addi tion, use of an Al0.25In0.75P Schottky layer increased the Schottky ba rrier height. Devices having 0.5 mum gate-length showed g(m) of 520 mS /mm and I(max) of 700 mA/mm. The gate-drain (BV(g-d)) and source-drain (BV(d-s)) breakdown voltages were as high as -14 and 13 V, respective ly. An f(T) of 70 GHz and f(max) of 90 GHz were obtained.