Interface Charge Effects on 2-D Electron Gas in Vertical-Scaled Ultrathin-Barrier AlGaN/GaN Heterostructure

Abstract

The combination of ultrathin-barrier (UTB) AlGaN (<6 nm)/GaN heterostructure and a charge-modulated SiNₓ grown by low-pressure chemical vapor deposition (LPCVD) is a promising technique for development of GaN-based millimeter-wave power amplifiers and recess-free enhancement-mode (E-mode) power switches. The LPCVD-SiNₓ passivation is capable of inducing high density of positive charges at the SiNₓ/(Al)GaN interface (~3.50 x 10¹³ cm⁻²), ensuring efficient recovery of 2-D electron gas (2-DEG) density that is comparable with conventional AlGaN/GaN heterostructure. Temperature-dependent Hall measurements and scattering mechanism simulations confirm the positive interfacial charges as well as interface states with density below 10¹³ cm⁻² and exert weak remote coulombic scattering of 2-DEG in metal-insulator-semiconductor heterojunction field-effect transistors (MIS-HFETs), which warrants a low on-resistance of UTB-AlGaN/GaN-based devices. UTB-AlGaN (<6 nm)/GaN heterostructure with LPCVD-SiNₓ passivation is a compelling technology platform for fabrication of high-frequency power amplifiers and high-efficiency E-mode power switches.