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The characteristics of different GaN transistor devices characterized at elevated temperatures for power applications are compared in this paper. High temperature characteristics of GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) and GaN high electron mobility transistors (HEMTs) are reported. For MOSFETs, the transconductance current (gm) increases with temperature, while for HEMTs is reduced. Their specific on resistance (Ron) follows the same trend. Specific contact resistivity (ρc) to implanted Si N+ GaN also diminishes with T, whereas for AlGaN/GaN ρc remains practically constant. We bring a more physical insight into the temperature behavior of these GaN devices by means of physics-based modeling in Sec. VI of this paper. The MOSFET’s field-effect mobility increases with T due to interface trap Coulomb scattering. Analogously, the HEMT’s gm decrease with T is attributed to a significant reduction in the two-dimensional electron gas carrier mobility due to polar-optical-phonon scattering. Simplified analytical expressions are presented for carrier mobility versus temperature which can be included in simulation packages.

Lateral n-channel enhancement-mode GaN metal-oxide-semiconductor ͑MOS͒ 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.

Rapid thermal processing (RTP) has been evaluated as an alternative to conventional furnace technique for oxynitridation of 4H-SiC. Nitrous oxide (normalN2O) under atmospheric pressure conditions was used as oxidizing gas. The beneficial effect of high energy photons, coming from the RTP halogen lamps, leads to an enhancement of the normalN2O molecule dissociation and an augmentation of the diffusion rate of dissociated species in the growing oxide. Compared to classical normalN2O oxidation, the net effect is not only to increase the growth rate but also to result in dielectrics that exhibit a reduced trapped charge, a more stable oxide/4H-SiC overall structure, and a better (less defective) interface. Further optimization, combined with a better understanding of the normalN2O rapid thermal oxidation process, should provide new issues for the growth of gate oxides in the SiC microelectronic industry.