The influence of group V:III flux ratio on the molecular beam epitaxy growth process of AlGaAs/GaAs quantum wells is studied by means of photoluminescence, using a careful line shape analysis. Upon enlarged group V flux, a sublinear increase of the growth rate and a reduction of shallow impurity incorporation is found, with, however, an increase of deep trap concentration, attributed to EL2.

Growth kinetics, impurity incorporation, defect generation, and interface quality of molecularbeam epitaxy grown AlGaAs/GaAs quantum wells: Role of group III and group V fluxes J. Vac. Sci. Technol. B 7, 704 (1989); 10.1116/1.584629Influence of the As:Ga flux ratio on growth rate, interface quality, and impurity incorporation in AlGaAs/GaAs quantum wells grown by molecular beam epitaxy Appl.Impurity trapping, interface structure, and luminescence of GaAs quantum wells grown by molecular beam epitaxy Appl.

A systematic knowledge of the influence of molecular-beam epitaxy growth parameters on the properties of AlGaAs/GaAs quantum wells grown under realistic growth conditions is important in order to obtain optimal performance of modern electronic and optoelectronic devices. Photoluminescence (PL) was used to investigate the influence of the Ga-controlled growth rate in the range below standard growth rates of 1 μm/h down to 0.1 μm/h, and of the As:Ga beam equivalent pressure ratio in the range of 10 to 60, on the growth kinetics, the interface quality, and the impurity incorporation, at a substrate temperature Ts =620 °C. As compared to in situ reflection high-energy electron diffraction (RHEED) measurements, where no sample rotation is possible, PL has the advantage that realistic growth conditions can be used. A careful line shape analysis, together with infrared and time-resolved PL measurements gives information on the interface roughness, the impurity incorporation, and the deep trap concentration. Non-negligible desorption of Ga during growth is found for the range of conditions under study. The desorption is found to increase upon a decrease of As:Ga ratio. The interface roughness as well as the impurity and trap incorporation are found to decrease with decreasing growth rate, an optimum interface quality being obtained below 0.5 μm/h. At this optimal growth rate, increasing the As4:Ga ratio leads to a decrease of shallow impurity concentration and thus to a narrower line width, but to a simultaneous increase of defect generation. Optimal growth conditions are found at a beam equivalent pressure ratio of 15. The observed desorption kinetics and interface properties can be explained in accordance with existing theoretical simulations. Finally, growth interruption was found to lead to optimal formation of flat growth islands when the overall growth rate is lowered.

Normal and inverted interfaces of GaAs/AlGaAs heterostructures are studied by comparing the luminescence of quantum wells (QWs) grown by molecular-beam epitaxy with a 10–300 s growth interruption either at one or both of the interfaces. The influence of growth interruption time on the incorporation of shallow impurities and traps and on the variation of the interface structure is investigated. GaAs surfaces become appreciably smoother with increasing interruption time, and increasing incorporation of shallow impurities, but no incorporation of traps at the growth surface is observed. At AlGaAs surfaces, the concentration of traps strongly increases with growth interruption time, but the surface does not become smoother. Additionally strong accumulation of shallow impurities at the inverted GaAs-on-AlGaAs interface is directly visualized.