Impact of barrier thickness on the strain effect in ZnSe/ZnS multiple quantum well structure

Abstract

Investigation on the impact of barrier thickness and the strain effect in band edges of wide band gap II–VI ZnSe/ZnS strained multiple quantum well structures (MQW) were carried out. QW structures were prepared by thermal evaporation technique by successive deposition of ZnSe and ZnS layers. The well ordered QW structure periodicity and interface abruptness were observed in small angle X-ray scattering. The formation of ZnSe/ZnS QW structures were identified from HRXRD peak position. The calculated lattice constant shows the presence of compressive strain in the ZnSe layers. Optical absorption measurements were carried out to study the strain effect on the band offset of ZnSe/ZnS MQW structure. The type I QW system were identified from the position of band onset. The observed blue shift of the QW in the absorption measurements were interpreted in terms of strain and quantum confinement effect followed by calculated band offset values using model solid theory. In 10nm barrier structure, a thickness fluctuation at the interface and strain causes the blue shift in the absorption onset than the quantum confinement was found. In 20 and 50nm structure the blue shift is due to confinement effect was observed.