Optical Transitions in Strained Layer InxGa1−xAs/InP Quantum Wells

We present a study of the optical transitions between confined particle states of strained layer quantum wells (SLQWs). SLQWs of InxGa1−xAs/InP with x ranging from 0 to 1 are an excellent system for this type of study because their strain varies systematically from −3.8%(x = 0) to +3.2%(x = 1). In previous studies we have used electro-optic techniques [1,2] and admittance spectroscopy [3] to show that most of the change with x in the band gap discontinuity between InP and InxGa1−xAs layers, takes place in the conduction band. A simple phenomenological deformation potential model, has enabled us to successfully calculate the lowest ( n = 1 ) excitonic transitions for any x and in particular to explain a type I to type II superlattice transition for x ≅ 0.2. In this study we show that in order to account for higer order transitions one has to include non-linear terms in strain and band non-parabolicity effects. Our model which contains no adjustable parameters agrees well with the observed transitions.