No abstract

Data are presented on the conversion (selective conversion) of high-composition (AlAs)x(GaAs)1−x layers, e.g., in AlxGa1−xAs-AlAs-GaAs quantum well heterostructures and superlattices (SLs), into dense transparent native oxide by reaction with H2O vapor (N2 carrier gas) at elevated temperatures (400 °C). Hydrolyzation oxidation of a fine-scale AlAs(LB)-GaAs(Lz) SL (LB +Lz≲100 Å), or random alloy AlxGa1−xAs (x≳0.7), is observed to proceed more slowly and uniformly than a coarse-scale ‘‘alloy’’ such as an AlAs-GaAs superlattice with LB + Lz≳200 Å.

The process of impurity-induced layer disordering (IILD) or layer intermixing, in Alx Gal _ x As-GaAs quantum well heterostructures (QWHs) and super lattices (SLs), and in related III-V quantum well heterostructures, has developed extensively and is reviewed. A large variety of experimental data on IlLD are discussed and provide newer information and further perspective on crystal self-diffusion, impurity diffusion, and also the important defect mechanisms that control diffusion in Alx Gal _ "As-GaAs, and in related IlI-V semiconductors. Based on the behavior of Column III vacancies and Column III interstitials, models for the crystal self-diffusion and impurity diffusion that describe ULD are reviewed and discussed. Because impurity-induced layer disordering has proved to be an important method for III-V quantum well heterostructure device fabrication, we also review the application of IILD to several different laser diode structures, as well as to passive waveguides. We mention that it may be possible to realize even more advanced device structures using IILD, for example, quantum well wires or quantum well boxes. These will require an even greater understanding of the mechanisms (crystal processes) that control IILD, as well as require more refined methods of pattern definition, masking procedures, and crystal processing.

Data are presented showing that Zn diffusion into an AlAs-GaAs superlattice (41 Lz∼45-Å GaAs layers, 40 LB∼150-Å AlAs layers), or into AlxGa1−xAs-GaAs quantum-well heterostructures, increases the Al-Ga interdiffusion at the heterointerfaces and creates, even at low temperature (<600 °C), uniform compositionally disordered AlxGa1−xAs. For the case of the superlattice, the diffusion-induced disordering causes a change from direct-gap AlAs-GaAs (Eg∼1.61 eV) to indirect-gap AlxGa1−xAs (x∼0.77, EgX∼2.08 eV).