Free-exciton spectra in heteroepitaxial ZnSe/GaAs layers

The free-exciton photoluminescence (PL) and reflection spectra of metal-org anic vapor-phase-epitaxy grown ZnSe/GaAs epilayers with a thickness greater than that of the strain relaxation thickness were studied experimentally a nd theoretically for temperatures in the range T = 10-120 K. Calculations w ere performed in the framework of absorbing and reflecting dead layer model s, using single and two-oscillator models, birth including and neglecting s patial dispersion. The results rule out the explanation that the fine struc ture in the free-exciton PL spectra derives from thermal strain splitting a nd polariton effects, if this structure is Mt accompanied by a correspondin g structure in reflection. It was shown that this structure in the PL spect rum originates mainly from Light interference caused by the presence of a d ead layer in the near-surface region, with the thickness of the dead layer depending on the excitation intensity. A correlation between the measured a nd inherent free-exciton spectra was established.