A GaAs power FET with zero-temperature-coefficient

A GaAs power FET with zero-temperature-coefficient has been developed for the first time. We found drain current (Id) and threshold voltage (Vth) shifts are strongly dependent on the mechanical stress inside a chip which generates piezoelectric charges in the channel. Such stress is originally caused by the difference of the thermal expansion coefficients of GaAs and base-metal. The sign of piezoelectric charge distribution can be controlled by the tensor product of the stress and crystal orientation. Using this inherent feature of GaAs material, we have developed a new temperature compensation technique of GaAs power FET just by choosing a proper gate orientation.