Formation of cavities in GaAs and InGaAs

Abstract

The ion implantation of He is examined as a means to form thermally stable cavities in GaAs. Room-temperature implantation of 2–10 × 10 16 He/cm 2 at 40 or 50 keV forms bubbles, but subsequent annealing at 250°C or above leads to exfoliation of the implanted surface layer. The exfoliation appears related to the agglomeration of bubbles on dislocations at the back of the layer; evidence suggests these may be misfit dislocations formed to relieve compressive stress in the implanted layer. Implantation of He at 150°C produces similar results, whereas the He diffuses out of GaAs without forming cavities during implantation at 300°C. However, implantations of immobile Ar followed by He at 400°C produce extended defects with bubbles in the implanted layer; the He can be degassed by subsequent annealing at 400°C to produce 1.5–3.5 nm cavities that are stable at this temperature. The same treatment applied to an In 0.10Ga 0.90As/GaAs heterostructure produces larger cavities preferentially located on dislocations at the interface, with only slight reduction in strain of the epitaxial layer. The microstructures of both GaAs and the heterostructure clearly demonstrate an attractive interaction between bubbles or cavities and dislocations.