This paper presents a theoretical method for determining the valence-band off-sets (VBOs) at strained alloy type heterojunctions, and applies it to InxGa1-xAs/GaAs system. Two strain conditions are studied: using the InxGa1-xAs as substrate and using GaAs as substrate in pseudomorphic growth. It is found that the variation of the VBO with the alloy composition is very nonlinear and closely related to the strain condition. In the case of using the InxGa1-xAs as substrate, the topmost valence band state in the GaAs layers is higher than that in InxGa1-xAs layers. When the GaAs is used as substrate, however, the topmost valence band state in an InxGa1-xAs layer becomes higher than that in a GaAs layer. Our result for InAs/GaAs is consistent with XPS measurement. Our result for InxGa1-xAs/GaAs with x=0.15 is in good agreement with ab initio pseudopotential calculation within the virtual crystal approximation. © 1995.
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