LPCVD Grown Si-Doped $\beta$-Ga$_2$O$_3$ Films with Promising Electron Mobilities

Abstract

We systematically investigated the growth of Si-doped $\beta$-Ga$_2$O$_3$ films using LPCVD system, achieving high electron mobilities of 162 cm$^2$/V.s and 149 cm$^2$/V.s at carrier concentrations of $1.51 \times 10^{17}$ cm$^{-3}$ and $1.15 \times 10^{17}$ cm$^{-3}$, respectively, for homoepitaxial (010) $\beta$-Ga$_2$O$_3$ films grown on $\beta$-Ga$_2$O$_3$ substrates and heteroepitaxial (-201) $\beta$-Ga$_2$O$_3$ films grown on off-axis c-sapphire substrates with 6{\deg} miscut, representing the highest mobilities reported for LPCVD-grown $\beta$-Ga$_2$O$_3$ materials. Carrier concentrations were precisely tuned by varying SiCl$_4$ flow rates at a growth temperature of 1000{\deg}C, resulting in concentrations ranging from $1.15 \times 10^{17}$ to $1.19 \times 10^{19}$ cm$^{-3}$, as confirmed by both Hall and C-V measurements. The films exhibited high crystalline quality, confirmed by high-resolution XRD and Raman spectroscopy, indicating phase purity and structural integrity. Surface morphologies characterized by FESEM and AFM imaging showed a strong correlation between carrier concentrations and surface smoothness, with lower concentrations resulting in reduced RMS roughness. SIMS analysis revealed uniform Si incorporation, with low carbon, hydrogen, and chlorine impurities below detection limits, indicating high purity of the films. A high low-temperature peak mobility exceeding 843 cm$^2$/V$\cdot$s was achieved for (-201) $\beta$-Ga$_2$O$_3$ films at 80 K, highlighting the high purity and low compensation of these films. These findings emphasize the potential of LPCVD growth system for producing high-purity $\beta$-Ga$_2$O$_3$ films with thickness ranging between ~2.3-11.7 $\mu$m and faster growth rates (~4.7-17 $\mu$m/hr), promising transport properties, controllable doping, and scalability for developing high power vertical devices.