GaN metal-oxide-semiconductor field-effect transistor inversion channel mobility modeling

Abstract

Lateral n-channel enhancement-mode GaN metal-oxide-semiconductor (MOS) field-effect transistors and lateral capacitors have been fabricated on a p-type epi-GaN substrate semiconductor and electrically characterized at different temperatures. A clear positive behavior of the inversion channel mobility with temperature has been obtained. A physics-based model on the inversion charge and charge trapped in interface states characteristics has been used to investigate the temperature dependence of the inversion MOS channel mobility. The field-effect mobility increase with temperature is due to an increase in the inversion charge and a reduction in the trapped charge for a given voltage gate. Then, for larger gate bias and/or higher temperatures, surface roughness effects become relevant. The good fitting of the model with the experimental data leads us to consider that the high density of charged acceptor interface traps together with a large interface roughness modulates the channel mobility due to scattering of free carriers in the inversion layer. A closed form expression for the experimental inversion MOS channel mobility is proposed.