Thickness dependent surface morphologies and luminescent properties of ZnSe epilayers grown on (001) GaAs by metalorganic chemical vapor phase deposition

ZnSe epilayers were grown on (0 0 1) GaAs substrate by using metalorganic c hemical vapor phase deposition. The growth was carried out by first growing a 30 nm thick ZnSe buffer layer at a lower temperature of 360 degreesC, fo llowed by the main growth at 450 degreesC. Surface morphologies and photolu minescence (PL) of the ZnSe layers with various thicknesses were investigat ed. We found that the ZnSe buffer layer contains (1) high density of island s about SO nm in size and (2) low density of holes about 100-1500 nm in dia meter. These two features develop in different ways during the growth at hi gher temperature. The places containing small islands become rougher first and then smoother, with an increase in layer thickness. After the thickness exceeds 210 nm, the surface becomes atomically flat. The holes, however, f avor the three-dimensional growth mode and develop into growth hillocks. En ergy dispersive X-ray spectroscopy showed that the hole is mainly made up o f Ga-Se compounds, consistent with the earlier reports that Ga2Se3 compound s are the source for the growth of hillocks. PL study showed that the donor s, accepters and the Jeep level emissions associated defects are mainly con centrated at the GaAs/ZnSe interface. (C) 2001 Elsevier Science B.V. All ri ghts reserved.