Over 6 $\mu$m thick MOCVD-grown Low-Background Carrier Density (10$^{15}$ cm$^{-3}$) High-Mobility (010) $\beta$-Ga$_2$O$_3$ Drift Layers

TL;DR

This study demonstrates the growth of thick, low-background carrier density $eta$-Ga$_2$O$_3$ layers with high mobility and uniformity using MOCVD, achieving record device performance metrics without intentional doping.

Contribution

It introduces a method to grow thick, low-background $eta$-Ga$_2$O$_3$ layers with high mobility and uniform doping profiles using MOCVD, surpassing previous device performance records.

Findings

Achieved 6.3 μm thick $eta$-Ga$_2$O$_3$ layers with high mobility (~190 cm$^2$/Vs).

Demonstrated controlled background carrier density scaling without intentional dopants.

Fabricated vertical Schottky diodes with record-high breakdown voltage (~1.2 kV).

Abstract

This work reports high carrier mobilities and growth rates, simultaneously in low unintentionally-doped UID (10$^{15}$ cm$^{-3}$) MOCVD-grown thick $\beta$-Ga$_2$O$_3$ epitaxial drift layers, with thicknesses reaching up to 6.3 $\mu$m, using triethylgallium (TEGa) as a precursor. Record high room temperature Hall mobilities of 187-190 cm$^2$/Vs were measured for background carrier density values of 2.4 - 3.5$\times$10$^{15}$ cm$^{-3}$ grown at a rate of 2.2 $\mu$m/hr. A controlled background carrier density scaling from 3.3$\times$10$^{16}$ cm$^{-3}$ to 2.4$\times$10$^{15}$ cm$^{-3}$ is demonstrated, without the use of intentional dopant gases such as silane, by controlling the growth rate and O$_2$/TEGa ratio. Films show smooth surface morphologies of 0.8-3.8 nm RMS roughness for film thicknesses of 1.24 - 6.3$\mu$m. Vertical Ni Schottky barrier diodes (SBDs) fabricated on UID MOCVD material were compared with those fabricated on hydride vapor phase epitaxy (HVPE) material, revealing superior material and device characteristics. MOCVD SBDs on a 6.3 $\mu$m thick epitaxial layer show a uniform charge vs. depth profile of $\sim$2.4$\times$10$^{15}$ cm$^{-3}$, an estimated $\mu$$_{drift}$ of 132 cm$^2$/Vs, a breakdown voltage (V$_{BR}$) close to 1.2 kV and a surface parallel plane field of 2.05MV/cm without any electric field management - setting record-high parameters for any MOCVD-grown $\beta$-Ga$_2$O$_3$ vertical diode to date.