AlN barrier HFETs with AlGaN channels to shift the threshold voltage to higher positive values: a proposal

Abstract

The need for efficient power converters is currently a major driver of GaN-on-Si research activities. Among several areas, a large research field is the engineering of enhancement mode devices. Several solutions have been provided in the past. Yet, almost all solutions either lack the compatibility with epitaxy on Si substrates (which is a necessity in terms of cost) or suffer from low positive threshold voltages (V th ) below +1 V. In power applications, there is definitely a need for higher values of V th . In this paper, we propose the utilization of AlN barriers in conjunction with AlGaN channels to obtain V th values of more than +3 V while still maintaining the low power-switching losses obtained in GaN-based heterostructure field-effect transistors.

Threshold voltage controlled by gate area and gate recess in inverted trapezoidal trigate AlGaN/GaN MOS high-electron-mobility transistors with photoenhanced chemical and plasma-enhanced atomic layer deposition oxides

“…28,29) The threshold voltage that linearly shifted with recess depth owing to capacitance was inversely proportional to barrier thickness, which corresponded to the linear trends of experimental data in Fig. 5(c).…”

“…where Φ B is the Schottky barrier height, ΔE C the conduction band offset between the gate oxide and the GaN buffer, Δ the depth of the well in the conduction band below the Fermi level, σ pol,ox the polarization difference between the oxide and AlGaN barrier layers, C ox the oxide capacitance, σ pol,barrier the polarization difference between the barrier and buffer layers, and C B the barrier capacitance. 28,29) The threshold voltage that linearly shifted with recess depth owing to capacitance was inversely proportional to barrier thickness, which corresponded to the linear trends of experimental data in Fig. 5(c).…”

Review—Ultra-Wide-Bandgap AlGaN Power Electronic Devices

“…Several groups have previously reported on both experimental 25-32 and computational 14,33 work on Al y Ga 1-y N/Al x Ga 1-x N heterostructures. Among the experimental papers, the highest aluminum compo-Based on 500 K LFOM best sition reported was an AlN/Al 0.60 Ga 0.40 N barrier/channel structure; 32 in contrast, our focus is on heterostructures with channel Al composition >70%.…”

Ultra-wide band gap AlGaN polarization-doped field effect transistor

“…Ultra-wide band gap (UWBG) semiconductors are attractive for high voltage power electronics [1][2][3][4][5][6] and high power rf electronics because the power density of these devices is expected to scale aggressively with band gap energy (E g ). For example, the lateral figure-of-merit (LFOM) for power switching increases as the square of the critical electric field (E crit ), 5) implying that LFOM increases E 5 g .…”