P-Channel GaN FETs on Low-Doped Layers Enabled by Thermal Mg-Diffusion Process: Demonstration and Characterization

This work reports on the development of GaN-based p-channel FETs on low-doped (~ 1017 cm-3) p-GaN layers by exploiting enhanced ohmic contacts obtained with a post-growth thermal Mg-diffusion process. Two architectures were tested, namely 1) MESFETs and 2)MOSFETs. The presence of improved ohmic contacts on very low-doped layers reflects in highly ideal DC characteristics, showing an ION /IOFF > 106, excellent ohmic behavior, and ideal transfer characteristics. Temperature dependence of ID – VG characteristics showed highly stable VTH, while the ION is affected by the activation of the Mg dopants. Finally, a model for channel mobility was developed, resulting in an effective hole mobility of ~0.6 cm2 · V-1 · s-1. The results prove that the Mg-diffusion-enhanced ohmic contacts are extremely effective in enabling future p-channel GaN devices for fully GaN CMOS devices.