The proposed program is aimed at developing aluminum gallium nitride heterostructure devices for high temperature sensor and electronics applications. We will focus on the high electron mobility transistor (or HEMT) for use as a high temperature microwave device or as a sensitive ultraviolet detector. Gallium nitride has a large bandgap of 3.2 eV which gives it a greater breakdown voltage and a higher saturated electron velocity than gallium arsenide. In addition, it is stable in air to around 800oC which makes it ideal for high temperature HEMT device use. HEMT devices are excellent for both power and low noise amplification since they posses a high carrier concentration and enhanced carrier mobility. Their power and noise performance increases with the potential barrier at the heterostructure interface. A Phase I program is proposed to produce high n-doped good optical quality films using a unique atomic layer epitaxy approach. All the present day growth and doping procedures cannot produce low resistivity epilayers. A successful Phase I program combined with our demonstration of high quality films and enhanced electron mobilities in heterojunctions with aluminum concentrations less than 20% will form a strong basis for a Phase II HEMT fabrication effort.
