Existence of two critical layer thicknesses ofGaAs/InGaAs multi-quantum wells determined byphotoluminescence microscopy

摘要

We have evaluated the critical layer thickness (CLT) ofGaAs/InGaAs multi-quantum wells by means of photoluminescence (PL)microscopy using the scanning near-field optical microscope. Reduction ofthe PL intensity appears as dark lines along the <110> directions in the PLimage. These dark lines are attributed to misfit dislocations formed at theInGaAs/GaAs interfaces. The density of dark lines in the <110> directionsas a function of the total layer thickness shows the existence of two CLT’sfor the formation of misfit dislocations. The two distinct CLT’s areexplained in terms of the modified Matthews-Blakeslee model that includesa lattice frictional force proportional to the In mole fraction.