GROWTH OF SELF-ASSEMBLED INAS AND INASXP1-X DOTS ON INP BY METALORGANIC VAPOR-PHASE EPITAXY

The formation of self-assembled InAs and InAsxP1-x dots on InP has bee n studied, in particular with deposition conditions under which mainly coherent dots are developed. The samples were grown by metalorganic v apour phase epitaxy. Morphological investigations were performed by at omic force microscopy, with the instrument working in the contact mode as well as in the noncontact mode. Surface densities and height distr ibutions were extracted, as a function of growth conditions. In additi on, photoluminescence was used for investigations of the optical prope rties of capped InAs dots, formed under equivalent conditions. Compari sons between the two characterization techniques show a qualitative ag reement with respect to the density of dots as well as their size homo geneity. It is also indicated that dots of binary InAs can be formed a t deposition temperatures not higher than about 500 degrees C. Elevate d deposition temperatures in this process result in an unintentional a lloying mechanism due to exchange reactions at the interface, leading to the formation of ternary InAsxP1-x dots, which can be seen as a sim ultaneous increase in the energy of the light emission and the average dot size, indicating the widening of the energy gap in the quantum do ts, which counteracts the decreased energy quantization in the larger dots formed at higher temperatures. (C) 1998 Elsevier Science B.V. All rights reserved.