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 epil ayers grown on InP substrate by metal-organic chemical vapor deposition (MO CVD). 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 a nd 700 degrees C, respectively. The maximum degree of phase separation was obtained from the InAlAs epilayer grown at 565 degrees C. However, the maxi mum degree of ordering was obtained at the medium growth temperature. A rap id thermal annealing experiment showed a maximum band-gap shift of 78 meV a t 880 degrees C for 3 min. Transmission electron microscopy (TEM) showed th at the origin of the blue shift of the band-gap was the complete disappeara nce of ordering and most of the total band-gap reduction (approximate to 3/ 4) occurred by phase separation. (C) 1999 Elsevier Science S.A. All rights reserved.