Real-space electron transfer in III-nitride metal-oxide-semiconductor-heterojunction structures

Abstract

The real-space transfer effect in a SiO2∕AlGaN∕GaN metal-oxide-semiconductor heterostructure (MOSH) from the two-dimensional (2D) electron gas at the heterointerface to the oxide-semiconductor interface has been demonstrated and explained. The effect occurs at high positive gate bias and manifests itself as an additional step in the capacitance-voltage (C-V) characteristic. The real-space transfer effect limits the achievable maximum 2D electron gas density in the device channel. We show that in MOSH structures the maximum electron gas density exceeds up to two times that at the equilibrium (zero bias) condition. Correspondingly, a significant increase in the maximum channel current (up to two times compared to conventional Schottky-gate structures) can be achieved. The real-space charge transfer effect in MOSH structures also opens up a way to design novel devices such as variable capacitors, multistate switches, memory cells, etc.

Threshold voltage control with high-temperature gate-oxide annealing in ultrawide bandgap AlGaN-channel MOSHFETs

“…Further increase in the gate forward bias does not lead to the current increase due to limited 2DEG channel capacity and real-space charge transfer from 2DEG to the dielectric-barrier interface. 30) As seen from Fig. 3(a), the unannealed MOSHFET devices show a very large threshold shift compared to an HFET.…”

Analysis of transient behavior of AlGaN/GaN MOSHFET

“…However, there were some problems such as the g m decreased at large V GS and the threshold voltage (V th ) shifted after the bias stress. It has been pointed out that an additional two-dimentional electron gas (2DEG) is formed at the oxide/AlGaN interface at high positive gate bias [16]. If the interface quality is not good, the g m degradation is expected.…”

Analytical Evaluation of Energy and Electron Concentrations in Quantum Wells of the High Electron Mobility Transistors

“…One is the presence of wide bandgap, which leads to high breakdown voltages and high saturation velocity. Second it is the existence of many heterostructure with high conduction band-offset and high piezoelectricity, which results high sheet carrier densities [3] [4].…”