Formation of misfit dislocations in GaAs/InGaAs multiquantum wells observed by photoluminescence microscopy

We have investigated the formation mechanism of misfit dislocations of GaAs/InGaAs multiquantum well structures by means of photoluminescence (PL) microscopy using the scanning near-field optical microscope. In the PL images, dark lines appeared along both [110] and [(1) over bar 10] directions. From comparison with the surface topographic images, we found that these dark lines correspond to misfit dislocations, which give rise to nonradiative recombination centers in the InGaAs well. The density of dark lines in the <110> directions as a function of the total layer thickness shows the existence of two critical layer thicknesses for the formation of misfit dislocations. The two distinct critical thicknesses are explained in terms of the modified J. W. Matthews and A. E. Blakeslee, [J. Cryst. Growth 27, 118 (1974)] model in which a lattice frictional force proportional to the In mole fraction is taken into account. (C) 2002 American Institute of Physics.