Size and density control of MOCVD grown self-organised GaSb islands on GaAs

We examine the morphology of ultrathin GaSb layers grown by atmospheric pressure chemical vapour deposition on GaAs substrates. Atomic force microscopy is used as a primary characterisation tool. Growth experiments are carried out with V/III ratio and temperature optimised for growth of high quality GaSb. The effects of dilution rates of metalorganic precursors in hydrogen, and pulse growth durations are investigated as a means of controlling growth rate. Dilution rates used are up to forty times higher than those used for standard bulk growth, to enable longer and better controlled island growth. We have found the critical control parameters to be the dilution rate/deposition time ratio and the product of the same quantities. Minimum dimensions reproducibly obtained are about 100×80 nm at an island thickness of 5 nm, with densities controllable between 1 to 10×10¹³ m^-2. We relate these findings to the present theories of self-organised island growth and mention their relevance to composite structures for electronic and optoelectronic applications