Photoluminescence (PL) and stimulated emission of GaN/Si layers grown by MOVPE with AlN and AlGaN buffers have been investigated. It has been found that thermal annealing of samples in nitrogen gas flow leads to an increase of the PL efficiency of up to 20 times, with a thermal activation energy of this process of 3.1–3.4 eV. The annealing promotes a significant decrease of the non‐radiative center concentration and an increase of the number of shallow states. The laser action at λ = 377 nm under pulsed optical excitation was achieved at room temperature evidencing a high quality of the samples.
The free-exciton photoluminescence ͑PL͒ and reflection spectra of metal-organic vapor-phase-epitaxy grown ZnSe/GaAs epilayers with a thickness greater than that of the strain relaxation thickness were studied experimentally and theoretically for temperatures in the range Tϭ10-120 K. Calculations were performed in the framework of absorbing and reflecting dead layer models, using single and two-oscillator models, both including and neglecting spatial dispersion. The results rule out the explanation that the fine structure in the freeexciton PL spectra derives from thermal strain splitting and polariton effects, if this structure is not accompanied by a corresponding structure in reflection. It was shown that this structure in the PL spectrum originates mainly from light interference caused by the presence of a dead layer in the near-surface region, with the thickness of the dead layer depending on the excitation intensity. A correlation between the measured and inherent free-exciton spectra was established.
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