GaAs pseudomorphic HEMT with insulating gate films formed by P2S5/(NH4)2SX sulfurization of recessed GaAs surface

Direct sulfurization of GaAs surfaces by treatment with P2S5/(NH4)2SX 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/(NH4)2SX-treated GaAs provided a lower surface roughness and more Ga–S bonds than the traditional (NH4)2SX-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)2SX sulfurization simultaneously suppressed the drain-to-source current (Ids). 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 µs pulse I–V measurement results, P2S5/(NH4)2SX-treated GaAs MIS-like pHEMTs exhibited identical Ids 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