Volmer-Weber growth mode of InN quantum dots on GaN by MOVPE

The growth of indium nitride quantum dots on c-plane GaN/sapphire was investigated by metal-organic vapour phase epitaxy using in situ spectroscopic ellipsometry and ex situ atomic force microscopy. Using an ammonia stabilisation for temperatures above 500 degrees C desorption of InN structures could be prevented during cool down. At a growth temperature of 520 degrees C and a trimethylindium partial pressure of 0.5 Pa (V/III ratio of 5000) we observe growth without a wetting layer in the Volmer-Weber mode, indicated by the presence of InN quantum dots for sub-monolayer coverages and a constant ratio of quantum dot volume to total InN amount. At this transport limited growth regime the typical quantum dot density of 7.10(10) cm(-2) is independent from coverage. Coalescence occurs after 20 s growth time at an average structure diameter of 51 nm as expected for such a density. Smallest uncapped hexagonal structures are realised with an average diameter of 28 nm and a height of 3.1 nm. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim