RELAXATION IN TENSILE-STRAINED INALSB/INSB HETEROSTRUCTURES

X-ray diffraction has been used to measure the residual strain in In 1-xAlxSb (x=0.15-0.64) layers of thickness h=0.1 μm, grown epitaxially on (100) InSb substrates. The results for this tensile-strained system are compared with a well-studied compressive-strain system, viz., InGaAs/GaAs. Experimental evidence is presented which suggests that the strain relaxation mechanism in this system is different from that in InGaAs/GaAs. This includes an observed critical layer thickness (hc) which is about five times the hc given by the Matthews and Blakeslee [J. Cryst. Growth 27, 118 (1974)] type models and a measured relaxation coefficient which is quasilinear in h/hc for 5<h/h c<35. The results have also been compared with predictions of the Dodson-Tsao (DT) model [Appl. Phys. Lett. 51, 1710 (1987)] which fits well the quasilinear behavior of the relaxation coefficient. In addition, it is argued that the DT equation provides a generic model that is not restricted to dislocation-mediated strain relief. Other possible mechanisms of strain relaxation in InAlSb/InSb are discussed. © 1995 American Institute of Physics.