Low Leakage GaAs MESFET Devices Operating at 350C Ambient Temperature

GaAs MESFET devices were fabricated and tested at 350°C and exhibited excellent current saturation, low output conductance, and less than ?> 10 ?>A of substrate leakage current at 350°C. The total drain current at pinchoff was ?> 80 ?>A of which ?> 70 ?>A was due to gate leakage. This was accomplished with the use of an AlAs buffer which provides a high resistance layer in series with the substrate resistance and markedly decreases the source-drain current that can pass underneath the FET channel through the substrate at elevated temperatures.