Resonance optical spectroscopy of long-period quantum-well structures

Theory of specular light reflection from long-period quantum-well structures taking into account the exciton contribution to dielectric polarization has been developed for an arbitrary relation between the background refractive index in the well, n(a), and barrier-material refractive index n(b). General expressions for the optical reflection and transmission coefficients for a structure with N equidistant quantum wells are derived with the use of the Green's function and transfer matrix methods. Normal and oblique light reflectance spectra from II-VI-based heterostructures were found to reveal a bright interference pattern caused by the difference between n(a) and n(b). A comparison of the theory with experiment has yielded the dispersion of n(a) and n(b) within a broad wavelength range and the parameters of the quasi-two-dimensional heavy-hole exciton (e1-hh1), namely, the resonant frequency and the radiative and nonradiative damping rates. Reflectance spectra from resonant Bragg and quasi-Bragg structures with real exciton parameters are calculated, and the effect on these spectra of the refractive-index difference and the deviation from the Bragg condition is analyzed. (C) 1997 American Institute of Physics.