Reactive evaporation of SiOx films for passivation of GaN high-electron-mobility transistors

Abstract

The surface passivation effects of silicon suboxide (SiOx) prepared by the reactive evaporation of silicon monoxide in oxygen atmosphere on the performance of AlGaN/AlN/GaN high-electron-mobility transistors (HEMTs) have been investigated. SiOx films with different oxygen contents (1.10 ≤ x ≤ 1.71) and root-mean-square (RMS) roughnesses (0.55 ≤ RMS ≤ 1.01 nm) were prepared under residual pressures from 1 × 10-6 to 6 × 10-4 Torr. Hall measurements revealed obvious increases in the product of sheet carrier concentration and electron mobility after the passivation. Accordingly, increases in drain current and transconductance were observed for all the SiOx passivated HEMTs. Both the gate and drain leakage currents first decreased and then increased with the increase of oxygen content. The lowest gate leakage current was observed in the devices with SiO1.23 passivation, and it was almost 20 times lower than that of the unpassivated devices. The same devices also exhibited the lowest current collapse and off-state drain current. The variations in leakage currents as a function of the residual pressure were found to correlate with the surface roughness of the passivation layer. Finally, the breakdown voltage of the SiO1.23 passivated HEMTs increased to 151 V, up from 99 V in unpassivated devices.

An Overview on Analyses and Suppression Methods of Trapping Effects in AlGaN/GaN HEMTs

“…Surface passivation is determined to minimize the density of surface traps in the AlGaN/GaN HEMT, commonly used with SiN x or SiO 2 by metal-organic chemical vapor deposition (MOCVD), or plasma enhanced chemical vapor deposition (PECVD) in past years [75]- [79]. To pursue superior passivation effect, a in situ passivation by molecular beam epitaxy (MBE), PECVD and plasma enhanced atomic layer deposition (PEALD) are further proposed to insulate the contact of air atmosphere [80], [81].…”

Optimization of passivation in AlGaN/GaN heterostructure microwave transistor fabrication by ICP CVD

“…As noted above an efficient tool for handling the abovementioned problems in AlGaN/GaN HEMT fabrication is surface passivation [10]. Passivating layers for AlGaN/ GaN HEMT can be a wide variety of relatively new dielectric materials (Al 2 O 3 , HfO 2 and ZrO 2 ) most of which are produced by atomic layer deposition, as well as dielectrics that are widely used in electronics (SiO x , SiN x , SiO x N y ) [11].…”