TEMPERATURE-DEPENDENT RELAXATION AND GROWTH PHENOMENA IN STRAINED INXGA1-XAS LAYERS GROWN ON GAAS

A series of InxGa1-xAs/GaAs layers with x ranging from 0.36 to 1 was grown by molecular-beam epitaxy, in order to examine the dependence of the critical layer thickness (CLT) on the In mole-fraction and growth temperature. Reflection high-energy electron diffraction (RHEED) and photoluminescence (PL) measurements were used and indicated a reduced CLT with increasing substrate temperature. A large difference in CLT was found between layers examined by RHEED and PL. This is discussed and explained to be a consequence of the difference in layer structure between layers examined by PL and by RHEED. While RHEED is a surface sensitive method, the luminescence in PL experiments originates from embedded layers. In PL measurements the thickness of the onset of three-dimensional growth, t3D, decreased from 55 to 15 angstrom for In0.36Ga0.64As layers as the growth temperature increased from 470 to 570-degrees-C. The PL study also indicated a reduced temperature dependence with increasing In content. The RHEED measurements for In0.36Ga0.64As showed that the thickness when the surface lattice parameter becomes equal to that of the alloys varied from 95 to 10 angstrom for growth temperatures between 490 and 590-degrees-C, respectively. Calculations by the most frequently used models for estimating the CLT were also carried out, The model of Price [Phys. Rev. Lett. 66, 469 (1991)] best fits our experimental results. The carrier mobility in 2-mum-thick InAs layers was measured between 20 and 300 K for layers grown at substrate temperatures between 390 and 525-degrees-C. The results indicate a peak mobility of 17 266 cm2/V s at 300 K for a structure grown at 520-degrees-C and a peak mobility at 77 K of 34000 cm2/V s for a sample grown at 510-degrees-C.