Comparison of the growth kinetics of In2O3 and Ga2O3 and their suboxide desorption during plasma-assisted molecular beam epitaxy

Abstract

We present a comprehensive study of the In2O3 growth kinetics during plasma-assisted molecular beam epitaxy and compare it to that of the related oxide Ga2O3 [P. Vogt and O. Bierwagen, Appl. Phys. Lett. 108, 072101 (2016)]. The growth rate and desorbing fluxes were measured during growth in-situ by a laser reflectometry set-up and line-of-sight quadrupole mass spectrometer, respectively. We extracted the In incorporation as a function of the provided In flux, different growth temperatures TG, and In-to-O flux ratios r. The data are discussed in terms of the competing formation of In2O3 and desorption of the suboxide In2O and O. The same three growth regimes as in the case of Ga2O3 can be distinguished: (i) In-transport limited, O-rich (ii) In2O-desorption limited, O-rich, and (iii) O-transport limited, In-rich. In regime (iii), In droplets are formed on the growth surface at low TG. The growth kinetics follows qualitatively that of Ga2O3 in agreement with their common oxide and suboxide stoichiometry. The quantitative differences are mainly rationalized by the difference in In2O and Ga2O desorption rates and vapor pressures. For the In2O, Ga2O, and O desorption, we extracted the activation energies and frequency factors by means of Arrhenius-plots.