AlxGa(1-x)N High Electron Mobility Transistors for High Temperature Applications

GaN high electron mobility transistors or HEMTs are proposed for use as high temperature electronic devices. HEMTs are excellent for both power and low noise amplification since they posses a high carrier concentration and an enhanced carrier mobility. GaN has a large bandgap of 3.2 a, which gives it a greater breakdown voltage and a higher saturated electron velocity than GaAs. GaN, in addition, is stable in air to ground 800 degrees C which makes it Ideal for high temperature use. High quIaity GaN films can be deposited using LPMOCVD on sapphire. This technique Is commonly used for GaAs epitaxy and has been used on a production level. We have previously demonstrated during a SBIR phase I program enhanced electron mobiIities in AIGaN/GaN hetrojunctions. In addition, we have fabricated point contact diodes using GaN that operated at temperatures as high as 700 degrees C. The proposed Phase I program will evaluate the high temperature chracteristics of AlGaN HEMT layers and demonstrate the necessary fabrication procedures needed for the HEMT device. In Phase II, ALGaN HEMT layers will be grown, fabricated and tested at elevated temperatures greater than 400 degrees C. These devices will then be used to fabricate an operational amplifier capable of operating at 325 degrees C.