Electrical and Structural Properties of In-Situ MOCVD Grown Al$_2$O$_3$/$\beta$-Ga$_2$O$_3$ and Al$_2$O$_3$/$\beta$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs

TL;DR

This paper explores how in-situ MOCVD-grown Al₂O₃ dielectrics on β-Ga₂O₃ and its alloys affect electrical and structural properties, revealing temperature and composition-dependent performance improvements for high-power MOSCAPs.

Contribution

It demonstrates the impact of growth temperature and Al composition on the electrical and structural quality of Al₂O₃/β-Ga₂O₃ MOSCAPs, highlighting optimized conditions for high-power device applications.

Findings

Higher growth temperature (900°C) improves crystallinity and interface sharpness.

Increased Al composition reduces carrier concentration and enhances breakdown fields.

Al₂O₃/β-Ga₂O₃ MOSCAPs exhibit high breakdown fields suitable for power electronics.

Abstract

This study investigates the electrical and structural properties of MOSCAPs with in-situ MOCVD-grown Al$_2$O$_3$ dielectrics on (010) $\beta$-Ga$_2$O$_3$ and $\beta$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ films. The Al$_2$O$_3$/$\beta$-Ga$_2$O$_3$ MOSCAPs showed a strong dependence on Al$_2$O$_3$ deposition temperature. At 900$^\circ$C, reduced voltage hysteresis ($\sim$0.3 V) and improved reverse breakdown voltage (74.5 V) were observed, with breakdown fields of 5.01 MV/cm in Al$_2$O$_3$ and 4.11 MV/cm in $\beta$-Ga$_2$O$_3$. At 650$^\circ$C, higher hysteresis ($\sim$3.44 V) and lower reverse breakdown voltage (38.8 V) were observed, with breakdown fields of 3.69 MV/cm in Al$_2$O$_3$ and 2.87 MV/cm in $\beta$-Ga$_2$O$_3$. However, forward breakdown fields improved from 5.62 MV/cm (900$^\circ$C) to 7.25 MV/cm (650$^\circ$C). STEM revealed improved crystallinity and sharper interfaces at 900$^\circ$C, enhancing reverse breakdown performance. For Al$_2$O$_3$/$\beta$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs, increasing Al composition ($x$ = 5.5\% to 9.2\%) reduced carrier concentration and improved reverse breakdown fields from 2.55 to 2.90 MV/cm in $\beta$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ and 2.41 to 3.13 MV/cm in Al$_2$O$_3$. Forward breakdown fields in Al$_2$O$_3$ improved from 5.0 to 5.4 MV/cm as Al composition increased. STEM confirmed compositional homogeneity and excellent stoichiometry of Al$_2$O$_3$ and $\beta$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ layers. These findings highlight the robust electrical performance, high breakdown fields, and structural quality of Al$_2$O$_3$/$\beta$-Ga$_2$O$_3$ and Al$_2$O$_3$/$\beta$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs for high-power applications.