Metal Organic Chemical Vapor Deposition 2

Abstract

This chapter reviews the heteroepitaxial growth of $\upalpha$- , $\upbeta$- , and $\upvarepsilon$-gallium oxide (Ga$_2$O$_3$)  films, with a focus on those grown using the metalorganic chemical vapor deposition (MOCVD) technique. Variations in growth conditions and substrates result in the growth of different polymorphs of Ga$_2$O$_3$  or combinations of them. $\upbeta$-Ga$_2$O$_3$ is consistently reported as the dominant phase to grow at high substrate temperatures >700 $^{\circ }$C. At lower substrate temperatures, $\upalpha$- and $\upvarepsilon$- metastable phases have been observed. Other growth conditions and substrates that have yielded $\upalpha$- and $\upvarepsilon$-Ga$_2$O$_3$ epitaxial films are also discussed. Doping of MOCVD-grown $\upbeta$-Ga$_2$O$_3$ is also briefly reviewed, where Si and Sn are the most commonly used dopants. Doping concentrations between $1\times 10^{17}$ and $8\times 10^{19}$ cm$^{-3}$ have been achieved, with corresponding electron mobility values between $\sim$130 and 50 cm$^2$/Vs.