Formation Mechanism of InP Films by Phosphidation under Controlled Chemical Potential and Wetting Behavior

The recent developments on the templated liquid-phase (TLP) growth process of the growth enabled bottom-up synthesis of indium phosphide (InP)-based optoelectronic devices on any kind of substrate. The precursors for the TLP growth of InP have SiOx/In/underlying-layer structures, where SiOx prevents dewetting of liquid In during the process. Sarkar et al. successfully modeled confined wetting of liquid In sandwiched by SiOx and various materials, but there were two notable exceptions in the model: Mo and MoOx. In this study, we thus systematically investigate the phosphidation behavior of the SiOx/In/Mo-related-layer samples. On the basis of the experimental results and the thermodynamic calculations, we discover unrecognized roles of the SiOx capping layer and MoOx underlying layer as follows: the SiOx layer reduces the chemical potential of phosphorus, and the MoOx layer is completely wettable with liquid In. Consequently, even without any capping layers, uniform InP films can be formed on any kind of substrate by phosphidation of In/MoOx stacked films using phosphorus sources with moderate chemical potential of phosphorus such as P4 gas generated from Sn/Sn4P3 binary composites. This study thus paves the way for more simplified processes of InP-based optoelectronic devices on nonepitaxial substrates.