Modelling of strained ZnSSe on relaxed ZnSSe-based structures for blue light emission

Abstract

It has been a long time since the start of successful production in laboratory of light-emitting devices based on wide bandgap II–VI semiconductors, but the applications have been limited by the luck of materials that can emit blue light efficiently. In this work, we propose and model a ZnS x Se 1− x -based structure emitting blue light and resolve many defect problems due to the lack of substrates of ZnSSe-epitaxy. The optoelectronic properties of (n-ZnS 0.8Se 0.2-relaxed/(ZnSe/ZnS 0.2Se 0.8/ZnSe)-strained/n-ZnS 0.8Se 0.2-relaxed) and (n-ZnS 0.8Se 0.2-relaxed/triple quantum well (QW) (ZnSe/ZnS 0.2Se 0.8/ZnSe)-strained/ n-ZnS 0.8Se 0.2-relaxed) are studied and compared. The numerical self-consistent resolution of Schrödinger–Poisson equations leads to the potential profiles of conduction and valence bands. Variation of ZnSe /ZnS 0.2Se 0.8/ZnSe well thickness permits to optimize the confinement of electrons and heavy holes, the wave function overlap, the oscillator strength and the carrier density for the two structures. The optimized results show that pure blue light emission is achieved more efficiently with the second proposed stack using a triple ZnSe/ZnS 0.2Se 0.8/ZnSe QW in the active layer.