Photo-assisted metal-organic vapour phase epitaxy of zinc chalcogenides

Abstract

Low-temperature growth is one of the key factors in obtaining high-quality epilayers of II–VI semiconductors. Metal–organic vapour phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) have successfully performed low temperature growth, and the crystalline quality has gradually been improved by optimizing the growth conditions. In the MOVPE growth of zinc chalcogenides, the growth temperature was below 300°C when using alkylzinc and hydrochalcogens as group II and group VI precursors, respectively [1–8]. However, these precursors cause room-temperature pre-reactions, resulting in poor surface morphology and crystallinity unless special care is taken in the gas-supplying techniques and low-pressure growth. Further, hydrochalcogens have very high toxity (H₂Se has a similar LD₅₀ value to AsH₃). In order to overcome these problems, alkyl or heterocyclic compounds of chalcogens have been developed as novel precursors, but the growth temperature must be as high as 500°C [9–12]. The photo-assisted technique, therefore, is a promising tool for reduction in growth temperature and for obtaining high-quality epilayers when using these source combinations. By this technique, selective growth or selective doping can also be expected.