MEASUREMENT OF THE CRITICAL THICKNESS OF ZNCDSE QUANTUM-WELLS IN ZNSEBARRIER LAYERS BY THE PIEZOELECTRIC EFFECT

The occurrence of the piezoelectric effect in a strained zincblende se miconductor layer grown on an (h11) plane results in an internal elect ric field which can be observed through the optical properties. We rep ort a study of Zn0.85Cd0.15 Se/ZnSe quantum wells grown on (211)B GaAs substrates where the quantum confined Stark effect due to the interna l field shifts the luminescence to longer wavelengths provided that th e quantum well layer is strained. When the well width is greater than the critical thickness the layer begins to relax and the internal fiel d decreases. We have used these measurements to determine that the cri tical thickness for the onset of strain relaxation of the Zn0.85Cd0.15 Se quantum wells grown on (211) oriented substrates is 20 nm. The met hod will be applicable to materials such as the nitride semiconductors with wurtzite symmetry. (C) 1998 American Institute of Physics. [S000 3-6951(98)03847-9].