COMPARISON OF THE CRYSTALLINE QUALITY OF STEP-GRADED AND CONTINUOUSLYGRADED INGAAS BUFFER LAYERS

In this paper we summarize work carried out to investigate the relaxat ion of epitaxial strained layers of InGaAs on GaAs, where the InGaAs c omposition has been increased throughout the layer in either a stepwis e or linearly graded form. The results are presented from the viewpoin t of exploiting the relaxed layers to provide prescribed in-plane surf ace lattice parameters for subsequent use as ''virtual'' substrates fo r novel devices. We compare the behaviour of step-graded and linearly graded InGaAs layers, We consider the crystalline quality of different structures and discuss the design requirements for subsequent device quality growth.