Sn-Doping in LPCVD-Grown (010) $\beta$-Ga${}_2$O${}_3$ Films

Abstract

In this work, Sn-doped (010) $\beta$-Ga${}_2$O${}_3$ homoepitaxial films were grown by low-pressure chemical vapor deposition (LPCVD), and the influence of Sn incorporation on their structural, morphological, and electrical properties was systematically investigated. Controlled room-temperature carrier concentrations ranging from $1.17\times 10^{17}$ to $3.06\times 10^{18}$ cm${}^{-3}$ were achieved, with corresponding Hall mobilities decreasing from 113 to 63 cm${}^2$ V${}^{-1}$ s${}^{-1}$. The films exhibited the monoclinic $\beta$-Ga${}_2$O${}_3$ phase, near-stoichiometric composition, and well-defined step-flow morphology, with a minimum rocking-curve FWHM of 68.4 arcsec and an RMS roughness of 2.63 nm. Film thicknesses ranging from 1.66 to 11.3 $\mu$m were obtained at growth rates of 6.4 to 16.6 $\mu$m h${}^{-1}$, demonstrating the ability of LPCVD to produce thick epitaxial layers. The sample with a room-temperature carrier concentration of $1.17\times 10^{17}$ cm${}^{-3}$ exhibited room-temperature and low-temperature Hall mobilities of 113 cm${}^2$ V${}^{-1}$ s${}^{-1}$ and 380 cm${}^2$ V${}^{-1}$ s${}^{-1}$ at 84 K, respectively. Both represent the highest reported values for LPCVD-grown Sn-doped $\beta$-Ga${}_2$O${}_3$. Transport modeling of the same sample yielded a shallow donor activation energy of 32.7 meV, a deeper donor level at 95 meV, and a low compensating acceptor concentration of $2.0\times 10^{16}$ cm${}^{-3}$, indicating efficient donor activation and a low degree of compensation. These results demonstrate that LPCVD enables controlled Sn doping while maintaining excellent structural and electrical quality, providing a viable route for realizing thick $\beta$-Ga${}_2$O${}_3$ epitaxial drift layers.