This work discusses the transition from high resistivity as-grown GaAs layers to thermally metastable low resistivity as-grown layers by molecular beam epitaxy. This transition occurs at about 430°C and coincides with a reflective high energy electron diffraction reconstruction change from a 2 × 1 to 2 × 4 pattern for an As4/Ga beam equivalent pressure ratio of 20. For growth temperatures in the range 350 to 430°C, room temperature Hall-effect measurements have shown resistivities of <107 ohm-cm and photoluminescence has shown new peaks at 0.747 eV and a band from 0.708 to 0.716 eV at 4.2K, in unannealed material.

We report on the design, construction, and implementation of the linear motion oven (LIMO), a translatable, elemental source for the generation of thermal molecular and atomic beams of varying incident flux at a fixed position substrate during vapor deposition processing. The robust and smooth relationship between oven position and incident flux, combined with the ease of rapidly and controllably varying the LIMO position, enables three important advances in vapor deposition technology. As demonstrated for an indium atomic beam source in a III–V molecular beam epitaxy growth process, the LIMO is found to provide for (1) controlled production of compositionally graded structures, (2) improved uniformity of flux at the substrate, and (3) complete elimination of conventionally troublesome flux transients.

We have employed a surface segregating population of Sb as an isoelectronic surfactant during solid-source molecular beam epitaxy (MBE) of AlGaAs layers. A steady-state population of Sb was maintained at the AlGaAs growth surface by providing a continuous Sb-2 flux to compensate for loss due to thermal desorption. A significant improvement in the optical quality of AlGaAs layers was observed by photoluminescence. Sharper GaAs QW. PL lines also indicate smoother inverted (GaAs on AlGaAs) interfaces when the Sb surfactant is employed. These improvements may be attributed to a reduced incorporation of impurities and point defects, and/or improved surface diffusion kinetics during AlGaAs MBE.

Solid source molecular-beam epitaxy was used to grow GaAsSb wells of various thicknesses with InAlAs barriers nominally lattice-matched to InP substrates. As-grown quantum wells (QWs) were measured by photoluminescence (PL) to have a monotonic increase in PL peak energy for a decrease in GaAsSb well thickness, indicating QW confinement. Growth interrupts at the GaAsSb/InAlAs interface, using arsenic and/or antimony overpressure, were found to degrade material quality as measured by PL. Thermal annealing up to the substrate growth temperature had no effect on the QW PL peak energies.

An exploratory study of the molecular-beam epitaxial growth and characterization of Er-doped GaAs and AlGaAs is described. Information regarding incorporation rate, diffusion, and surface riding of Er is obtained via secondary ion mass spectrometry and reflective electron diffraction measurements. Low temperature photoluminescence (PL) measurements near 1.54 μm show emission from multiple Er sites in AlGaAs:Er and GaAs:Er. Substrate temperature is found to affect PL spectra in a complicated manner. The dependence of Er-center PL intensity on Er concentration is very nonlinear and peaks at [Er]≊1019 cm−3. GaAs:Er samples with [Er]=6×1018 cm−3 are p type with room temperature hole concentrations of 2–5×1016 cm−3. Co-doping with Er and Si dramatically reduces electron concentration from that obtained with Si only, while the presence of Si reduces the Er-center PL intensity.

Surface composition is known to influence cation and anion incorporation rates (IRs) during III–V molecular beam epitaxy (MBE) at high growth temperatures. Consequently, IRs can vary at heterointerfaces. The present study examines the temporal behavior of IRs during formation of AlGaAs/GaAs, GaInAs/GaAs and GaAsSb/GaAs heterointerfaces. Incorporation rates are deduced from the in situ detection via desorption mass spectrometry of the non-incorporated, or desorbed, fraction of the incident beam. Predicted compositional profiles are calculated from the observed IR variations and show significant enrichment in composition of one of the constituent species at the heterointerface. The predicted compositional profile for the GaInAs/GaAs system is qualitatively verified by X-ray diffraction and photoluminescence measurements on separately grown structures. These results are interpreted on the basis of simple first-order desorption considerations which incorporate strain-dependent activation energies for desorption.