Dependence of electron mobility on epi channel doping in GaN MOSFETs

The field-effect mobility and Hall mobility of electrons in lateral, accumulation-mode GaN MOSFETs have been comparatively studied. The devices were fabricated on three different samples, sample A consisting of 70 nm n-type (N_D = 5×10¹⁷ cm^-3) GaN and sample B 0.5 μm unintentionally doped (N_D < 1×10¹⁶ cm^-3) GaN, both on 2 μm undoped Al_0.35Ga_0.65N grown on the n⁺-SiC substrates and sample C 3 μm unintentionally doped GaN on the sapphire substrate. The maximal field-effect mobilities are 120 cm²/V-s, 90 cm²/V-s and 53 cm²/V-s respectively in the three samples. The Hall mobility is also measured for samples A & B and reaches a maximal value of 160 cm²/V-s.