Observation of lattice relaxation at the GaAsP/GaAs interface beyond the critical thickness by transmission electron microscopy

The lattice relaxation at the GaAs1−xPx/GaAs interface is observed using thickness fringe images in transmission electron microscopy. The bending of the equal thickness fringes observed near the interface is explained, assuming that crystal planes are inclined near the interface and that the inclination has a maximum at the interface. The magnitudes of inclination and the thickness of the strained region are estimated for various phosphorous composition and the GaAsP thickness. The lattice relaxation mechanisms for GaAsP on GaAs is described. It is indicated from the thickness fringe observation that the lattice relaxation occurs gradually beyond the critical thickness.