The influence of substrate on the self-organised island nucleation and morphology of metalorganic chemical vapour deposited GaSb

Metalorganic chemical vapour deposition was used to compare initial growth and film evolution of GaSb on GaAs, Ge, InAs and GaSb under identical condi tions. These substrate-layer pairs allow the effects of lattice mismatch an d chemical compatibility to be differentiated. GaSb forms self-organised is lands on GaAs and Ge, where mismatches are each about 8%, but not on closel y lattice matched InAs and GaSb. Substantial differences were observed, how ever, between islands grown on Ge and GaAs, the former yielding fewer but l arger islands than the latter. For example growth for 30 s under optimised conditions gave typical island lateral dimensions of 150 nm with heights ar ound 35 nm on GaAs, but respective values of 250 nm and 70 nm on Ge. The vo lumetric growth rates suggest that nucleation in the GaSb/Ge system is slow er than previously reported island growth rates in the GaSb/GaAs system. Th icker layers grown on GaAs, GaSb and InAs show similar elongated pyramidal surface features with clearly visible facets, whereas growth on Ge results in a much smoother but irregular surface. Both of these characteristics are attributed to a closer chemical similarity in GaSb/GaAs than in the GaSb/G e system. (C) 1999 Elsevier Science B.V. All rights reserved.