PLASTIC VERSUS ELASTIC MISFIT RELAXATION IN III-NITRIDES GROWN BY MOLECULAR-BEAM EPITAXY

With a view to understand the misfit relaxation mechanisms for binary III-nitride semiconductors, a combined RHEED and TEM study of strain a ccommodation for AIN/GaN, GaN/AIN and InN/GaN MBE heteroepitaxial comb inations is presented. It is shown that AIN grows on GaN (2.7% tensile strain) in a two-dimensional way In accordance with a Frank-van der M erwe mode with plastic relaxation occurring through the formation of n oninteracting edge-type dislocations. On the other hand, GaN epitaxy o n AIN (2.7% compressive strain) proceeds in different modes according to the growth temperature: in particular, a strained Stranski-Krastano w mode can be evidenced at intermediate temperatures. For the case of InN on GaN (10% compressive strain), strain relaxation occurs through the formation of dislocated islands on the surface, i.e. through a rel axed Stranski-Krastanow mode. The implications of these: different gro wth processes to the development of nitride-based quantum dots heteros tructures are presented. (C) 1998 Elsevier Science B.V. All rights res erved.