GaAs substrate thermal preheating effect exerted on ZnTe epilayer

In this study, the role of the thermal preheating of the substrate in the physical properties of the epilayer has been systematically examined. ZnTe epilayers were grown on the GaAs(100) substrate at a temperature range of 450-630°C by hot wall epitaxy (HWE), and their structural and optical properties were measured by the double crystal rocking curve (DCRC) and photoluminescence (PL). The full-width at half-maximum (FWHM) values of DCRC were the smallest in the ZnTe epilayers grown on the GaAs thermally preheated at around both 510 and 590°C. However, at around 550°C they increased due to the reconstruction of the atoms in the surface, due to the oxide layer at below 490°C and due to the surface defects at above 610°C. It was observed from PL analysis that the FWHM values of the light-hole exciton X1s,1h and of the second-order Raman line increased at around 550°C. With increasing preheating temperature, the intensities of Y-bands and of the oxygen-bound exciton peak related to an oxide layer on the GaAs surface generally decreased. From these experimental results, it is shown that the crystal quality and the PL properties of ZnTe epilayers were enhanced for the GaAs substrates thermally preheated at 510 and 590°C.