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

Abstract

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.

Vertical heterojunction field‐effect transistors utilizing re‐grown AlGaN/GaN two‐dimensional electron gas channels on GaN substrates

“…In the case of inversion channel layers, electron mobility is degraded due to inversion channels of MOSFETs. In the case of inversion channel layers, electron mobility is degraded due to Coulomb and roughness scattering by the traps and roughness at the oxide/semiconductor interface [9]. On the other hand, for the 2DEG channel layer of our device, the channel mobility can be enhanced than the bulk mobility because the scattering centers are extremely low at the AlGaN/GaN heterojunction interface and ionized impurity scattering is reduced owing to their undoped nature.…”

Modeling the effect of thin gate insulators (SiO2, SiN, Al2O3 and HfO2) on AlGaN/GaN HEMT forward characteristics grown on Si, sapphire and SiC

“…This is due to the fact that the polarization field has a very weak dependence on the temperature and hence, n s is also a weak function of the temperature. It must be mentioned that, in many practical situations, there is a number of interface (Q it,MIS ) and/or bulk traps (Q ins ) created during insulator deposition [36]. This would provoke a shift of the threshold voltage towards more negative or more positive values (depending on the nature of these traps, acceptors or donor, positive or negative ions, etc.).…”

“…On GaN MOSFET devices, the density of interface traps (D it ) has a major affect on the onstate current of the device, as Coulomb scattering greatly reduces the field-effect mobility [36]. Within the MIS structure of GaN HEMTs, the presence of a large amount of interface traps have been extensively demonstrated [27,28].…”

AlGaN/GaN hybrid MOS-HEMT analytical mobility model

“…It has been proposed [10][11][12] mobility models for describing the mobility degradation observed in MOSFET devices due to Coulomb scattering effects at interface traps (l c ). Generally, in GaN and SiC MOSFETs this interface trap Coulomb scattering limiting mechanism is so relevant that the approximation l n (MOS-FET) ' l c could be used, in particular at the lower gate bias and at low temperature.…”

“…The mobility of carriers in the inversion channel of a MOSFET device is always a part of the carrier mobility in the semiconductor bulk (l B ). The widely accepted model consisting of the first three terms of (3) provides a good description of channel mobility for silicon MOSFETs [10]: …”