RAMAN-SCATTERING STUDY OF THERMAL INTERDIFFUSION IN INGAAS/INP SUPERLATTICE STRUCTURES

Interdiffusion process of InGaAs/InP superlattice structures by thermal annealing of 700-850-degrees-C is studied by Raman spectroscopy. Peak intensities and peak energies of InAs-, GaAs-, and InP-like longitudinal optical (LO) phonon modes change with thermal annealing temperature and time. Depth profiles of the group III and group V atoms are estimated quantitatively by measuring the variations of the peak energies of the LO phonon modes and the ratios of the mode intensities. The energy shift of the GaAs-like LO peak showing a small broadening, the existence of nonenergy shift InP LO phonon peak and the emerging of InP-like LO peak in the lower energy region indicate that the interdiffused superlattice consists of uniform compositional InGaAsP well and InP barrier layers and sharp interfaces. It is found that the resulting InGaAsP quaternary alloy is roughly lattice-matched to InP (< +/- 0.5%). It is also found that the diffusion coefficient in the well region is larger than that in the barrier region, and that the interdiffusion coefficient D0 and activation energy E(a) are 8.56 x 10(10) cm2/s and 5.82 eV, respectively. The interdiffusion in this superlattice is determined by the diffusion in the InP region.