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/sub D/ = 5/spl times/10/sup 17/ cm/sup -3/) GaN and sample B 0.5 /spl mu/m unintentionally doped (N/sub D/ < 1/spl times/10/sup 16/ cm/sup -3/) GaN, both on 2 /spl mu/m undoped Al/sub 0.35/Ga/sub 0.65/N grown on the n/sup +/-SiC substrates and sample C 3 /spl mu/m unintentionally doped GaN on the sapphire substrate. The maximal field-effect mobilities are 120 cm/sup 2//V-s, 90 cm/sup 2//V-s and 53 cm/sup 2//V-s respectively in the three samples. The Hall mobility is also measured for samples A & B and reaches a maximal value of 160 cm/sup 2//V-s.