Complex Airy analysis of photoreflectance spectra for bulk In/sub x/Ga/sub 1-x/As on InP and In/sub x/Ga/sub 1-x/As HEMTs

The authors present a detailed, first-principle analysis of photoreflectance (PR) spectra using complex Airy functions and their derivatives. With the use of the complex Airy functions, PR spectra directly yield band-gap energies (light and heavy hole). The proposed model considers three distinct but superimposed features in the PR spectra of InGaAs which represent the light and heavy hole bands and an exciton feature below the band-gap energy. The band-gap features are modeled using complex Airy functions and their derivatives and the dielectric function of the material. The complex Airy lineshapes are evaluated numerically and fit to the PR spectra using a sequential simplex procedure on a personal computer. The complex Airy lineshapes are applied to both intermediate electric field (Franz-Keldysh oscillations) and low field PR spectra, illustrating that complex Airy functional analysis represents a generalized treatment. The authors correlate energy from the PR spectral fits to those determined from photoluminescence measurements.<>