Two-dimensional arsenic-precipitate structures in GaAs

A technique is demonstrated to control the incorporation of excess arsenic and subsequent positioning of As clusters with coarsening anneals in AlGaAs/GaAs heterostructures. By growing at low substrate temperatures using molecular beam epitaxy, excess As can be incorporated in GaAs and AlGaAs epilayers. By switching the growth mode at these low substrate temperatures to migration enhanced epitaxy, close to stoichiometric epilayers can be obtained when the As flux is As4. Upon anneal, the As precipitates form preferentially in the GaAs regions, even if the as-grown GaAs regions were highly-stoichiometric and the as-grown AlGaAs regions contained an excess of As. However, the excess As can be contained in the AlGaAs regions, where it will form clusters with anneal, if thin AlAs As-diffusion barriers clad the AlGaAs regions. © 1993.