GaAs pseudomorphic HEMT with insulating gate films formed by P ₂S₅/(NH₄)₂S_X sulfurization of recessed GaAs surface

Direct sulfurization of GaAs surfaces by treatment with P₂S ₅/(NH₄)₂S_X was employed to yield gate insulating layers for a depletion-type recessed gate GaAs metal-insulator-semiconductor-like pseudomorphic high-electron mobility transistor (MIS-like pHEMT). The novel P₂S₅/(NH ₄)₂S_X-treated GaAs provided a lower surface roughness and more Ga-S bonds than the traditional (NH₄) ₂S_X-only sulfurized GaAs; these bonds improved device uniformity and reduced the surface states that are induced by native Ga-O bonds. The diffusion of S atoms from P₂S₅/(NH₄) ₂S_X sulfurization simultaneously suppressed the drain-to-source current (I_ds). The Schottky gate reverse leakage current was suppressed, resulting in a higher breakdown voltage, when this sulfurized GaAs insulator was used. Based on the dc and 1 νs pulse I-V measurement results, P₂S₅/(NH₄) ₂S_X-treated GaAs MIS-like pHEMTs exhibited identical I_ds trends; however, conventional NH₄OH-treated pHEMT exhibited an obvious decline in current upon pulse measurement because of the higher surface traps. These results were consistent with the characterization of this insulating film.