Observation of phase separation and ordering in the InAlAs epilayer grown on InP at the low temperature

We have studied the phase separation and ordering phenomenon of InAlAs epilayers grown on InP substrate by metal–organic chemical vapor deposition (MOCVD). From the intensity and full width half maximum FWHM of double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL), we observed that the structural and optical quality of InAlAs epilayers were improved as growth temperature increased. The band-gap reduction due to phase separation and ordering is 291, 246 and 28 meV in the InAlAs epilayers grown at 565, 615 and 700°C, respectively. The maximum degree of phase separation was obtained from the InAlAs epilayer grown at 565°C. However, the maximum degree of ordering was obtained at the medium growth temperature. A rapid thermal annealing experiment showed a maximum band-gap shift of 78 meV at 880°C for 3 min. Transmission electron microscopy (TEM) showed that the origin of the blue shift of the band-gap was the complete disappearance of ordering and most of the total band-gap reduction (≈3/4) occurred by phase separation.