Suppression of gate leakage current in n-AlGaAs/GaAs power HEMTs

Experiments of gate leakage current in a double-channel n-AlGaAs/GaAs FET with SiN_x film passivation indicated that the gate leakage current and its stability depend critically on the stoichiometry of the surface. The content of NH₄ OH in the etching solution prior to the SiN_x film deposition and the NH ₃/SiH₄ gas content ratio, particularly at the initial stage of plasma-CVD SiN, deposition, should be selected to minimize the surface state density of possible antisite defects. Extremely low gate leakage currents of 50 nA/mm have been obtained with an improved process, which is useful to realize low-distortion FETs