Thickness dependence of lattice parameter and band gap in Ga xIn 1−xAs 1−yP y/InP Heterostructures

Abstract

The liquid-solid phase diagram of the quaternary system GaInAsP has been calculated in order to grow Ga x In 1− x As 1− y P y layers on indium phosphide substrates by liquid phase epitaxy. Mixed compounds with an energy gap of 1.17 eV at 300 K and lattice-matched with the substrates have been obtained. The lattice parameter a was determined by X-ray diffraction. The energy gap E g was determined by photoluminescence or electro-reflectance at 300 K and studied as a function the thickness of the epilayer. variations of a have been observed by measuring the lattice parameter by X-ray diffraction for different hkl reflections. The measurements were shown to be depth dependent. The use of a double-reflection X-ray diffractometer with copper radiation confirms this dependence. Also, E g varied with thickness. The thickness dependence of the composition can be interpreted as an effect of diffusion-limited growth and phosphorus evaporation from the melts.