Fully quaternary In/sub 0.52/(Al/sub 1-x/Ga/sub x/)/sub 0.48/As/In/sub 0.53/(Al/sub x/Ga/sub 1-x/)/sub 0.47/As (x=0.1, 0.2) heterostructures on InP for HFETs

A fully quaternary (FQ-) In/sub 0.52/(Al/sub 1-x/Ga/sub x/)/sub 0.48/As/In/sub 0.53/(Al/sub x/Ga/sub 1-x/)/sub 0.47/As (x=0.1, 0.2) heterostructure was introduced into doped-channel FETs (FQ-DCFETs) on InP substrates. Based on our previous studies, we observed that by adding a small amount of Ga (10%) atoms into the InAlAs Schottky and buffer layers in the HEMT structure, device performance can be enhanced due to a better quality of InAlGaAs material. Furthermore, by adding a small amount of Al (10% or 20%) atoms into the InGaAs channel layers, the associated impact ionization process can be suppressed in this InAlGaAs channel, resulting in an enhancement of breakdown voltage. Therefore, in this report, we combined both techniques to realize the fully quaternary HFETs and characterize their performance.