Improvement of the breakdown voltage of GaAs-FETs using low-temperature-grown GaAs insulator

An as-grown GaAs layer grown by molecular beam epitaxy at low temperature (LT-) has been used as an insulator for power GaAs field effect transistors (MISFETs). It was found that the LT-GaAs layer successfully passivates the surface, of GaAs-FETs, eliminates the hysterisis of drain-source current, and improves the breakdown behaviour. The breakdown voltage, V/sub BD/, for MISFETs is as high as 40-50 V for 2 /spl mu/m spacing between the gate and drain contacts, and is independent of the doping-thickness product. V/sub BD/ also exhibits an increase on decrease of temperature, and suggests a high breakdown voltage in the high frequency domain. It is the particular electrical properties of the as-grown LT-GaAs layer which are found to be responsible for the superior properties of the LT-GaAs MISFETs. The LT-GaAs layer exhibits ohmic behaviour which leads to a linear distribution of electric field between the gate and drain. The dominant hopping conduction eliminates the concentration of injected electrons, while the high breakdown field of the LT-GaAs layer ensures a high breakdown voltage of LT-GaAs MISFETs.