Issues in molecular-beam epitaxy of ZnSe-based heterostructures for blue-green lasers

We first report on optical spectroscopy studies of homo-epitaxial ZnSe layers grown by molecular beam epitaxy on substrates prepared by solid-phase recrystallization. We identify the main residual impurities to be Li diffusing from the substrate, and Ga and In coming from the sample soldering before epitaxy. We show that ZnSe homoepitaxial layers are of higher structural quality than their counterparts grown directly on GaAs substrates. Their remarkable quality indicates that an “all II–VI” way might be desirable for blue-green laser diodes. In addition, we explore the possibility of using plasma-activated arsenic as a p-type dopant of ZnSe hetero-epitaxial layers. At the present stage our results lead to the conclusion that (i) even when activated via a plasma, as is difficult to incorporate into the growing ZnSe layers, and (ii) when it is actually introduced it gives rise to deep levels.