We have developed a process using molecular-beam epitaxy for growing GaAs/AlGaAs quantum wells with thicknesses and Al content that vary in a controlled manner on (100)-oriented GaAs substrates. The control is accomplished by manipulating the Ga sticking coefficient through local variations of the substrate temperature. To indicate the range of thickness and Al content variations that can be achieved, we show that exciton peak energies of the quantum wells can be made to vary as much as 200 meV between predetermined locations <2 mm apart on the wafer. The quality of the exciton spectra is good throughout, indicating good quality epitaxial layers throughout. This process allows flexibility in designing the well dimensions and composition in various regions of the wafer and could lead to a variety of important developments in GaAs devices.
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Goodhue et al. (1988) studied this question.