Plasma deposition of GaN/InP multilayer structures on Si

The fabrication of periodical GaN/InP structures on Si with a wide layer thickness variation (from submonolayer digital alloys to multilayer stacks) using low-temperature plasma technology is explored in the paper. The proposed technology, which combines the approaches of plasma-enhanced chemical vapor deposition (PECVD) and atomic-layer deposition, was realized at 380 °C using a standard capacitively coupled plasma PECVD reactor. Trimethylindium, trimethylgallium, phosphine, and nitrogen (N2) were used as sources of In, Ga, P, and N, respectively. A series of GaN/InP periodical structures were grown on an Si (001) substrate with a previously deposited thin (7 nm) GaP buffer layer. A structure grown as submonolayer digital alloys (a short-period superlattice with GaN and InP thicknesses of 0.3 and 0.6 nm) exhibits a crystal structure consisting of both microcrystalline and epitaxially oriented grains that follow the orientation of the Si substrate. The vertical size of the grains corresponds to the total GaN/InP periodical structure’s thickness. However, with an increase in the GaN barrier layer thickness to 1.5–3 nm, the GaN undergoes amorphization. This leads to the formation of a layered structure containing misoriented nanocrystalline InP layers embedded between amorphous GaN layers. This effect is associated with significant incorporation of phosphorus into GaN layers, which are formed using a N2 + H2 gas mixture plasma. Indeed, the H2 plasma used for GaN deposition interacts with the phosphorus deposited on the chamber wall during the previous InP step. The discovered issue should be taken into account for plasma technology development of multilayer structures, which included a combination of III-nitride/III-phosphide.