Plasma Enhanced Chemical Vapor Deposition of P-type Cu2O from Metal Organic Precursors

Abstract

The scope of this work was to optimise the reactant delivery parameters for the PECVD of p-type Cu2O films from Cu(hfac)(tmvs), with the aim to explore an alternative to other large area deposition techniques such as sputtering. Whilst n-type metal oxide semiconductors such as amorphous indium gallium zinc oxide have now been developed and offer significantly improved device performance over hydrogenated amorphous silicon, with devices achieving mobilities >10 cm2(Vs)-1, there is still an absence of good p-type inorganic semiconductors that provide similar performance. Cu2O is a promising p-type metal oxide, but there remain limitations on the industrial scalability of some of the deposition processes demonstrated so far. Plasma enhanced chemical vapor deposition (PECVD) has been scaled for uniform deposition on Generation 10 display glass (2.88m x 3.13m) and so provides a viable alternative. The Cu2O films deposited in this work achieved a Hall mobility of ~1cm2(Vs)-1 and were stable over a period of months. Contrary to previous reports of an 'incubation' period, the initial growth rate during and immediately following nucleation was (~40 nm/pulse) 10 times greater than the steady state growth (~4 nm/pulse) achieved later in the deposition. Topographical scaling methods and fractal analysis of the film surface morphology using atomic force microscopy, at different stages during growth development, link this shift to a regime transition from growth dominated by surface diffusion to volume diffusion.