P-channel GaN/AlGaN heterostructure junction field effect transistor

Several groups have demonstrated AlGaN/GaN based heterostructure field-effect transistors (HFETs) with record high saturation current in excess of 2 A/mm and RF output power levels of 5-12 W/mm (M. Asif Khan et al., in Encyclopedia of Materials: Science and Technology, Elsevier Science, pp. 2616-2631, 2001). However, to date p-channel transistors could not be fabricated due to poor doping of the AlGaN or GaN layers. In past, we have proposed hole accumulation layers that can be created at an AlGaN/GaN interface by using large bandgap offsets and the effect of piezo-doping in nitride based materials (M. Asif Khan et al., Appl. Phys. Lett., vol. 75, p. 2806, 1999; M.S. Shur et al., ibid., vol. 76, p. 3061, 2000). In this paper we for the first time report on a p-channel HJFET with the threshold voltage of around 8-10 V, which is close to that of typical n-channel HFETs. The AlGaN/GaN heterostructures were grown by metalorganic chemical vapor deposition on a basal plane of sapphire substrate.