Low-frequency noise in AlTiO/AlGaN/GaN metal-insulator-semiconductor field-effect transistors with non-gate-recessed or partially-gate-recessed structures

Abstract

We have systematically investigated low-frequency noise (LFN) in AlTiO/AlGaN/GaN metal-insulator-semiconductor field-effect transistors (FETs) with non-gate-recessed or partially-gate-recessed structures, where gate insulators using AlTiO, an alloy of Al2O3 and TiO2, are obtained by atomic layer deposition. For drain current LFN, we find pure spectra for the well-above-threshold regime, and superposition of and Lorentzian spectra near the threshold voltage. The Hooge parameters are evaluated from the contribution and found to be independent of the AlTiO thickness. However, the remaining AlGaN thickness strongly affects the Hooge parameter near the threshold voltage; in the low channel electron concentration regime of the partially-gate-recessed FETs, a smaller remaining AlGaN thickness gives a larger Hooge parameter proportional to the inverse of the electron concentration, indicating that channel electron number fluctuation dominates the Hooge parameter. We consider that the channel electron number fluctuation is caused by electron traps introduced by the recess etching process in the remaining AlGaN. On the other hand, the Lorentzian spectra give specific time constants almost independent of the AlTiO thickness and the remaining AlGaN thickness, corresponding to trap depths of 0.6–0.8 eV. This can be attributed to traps in AlTiO near the AlTiO/AlGaN interface.