Manganese diffusion in gallium arsenide, aluminum gallium arsenide, and gallium arsenide-aluminum gallium arsenide heterostructures

Abstract

While Zn, Be, C, and Mg have been commonly used as p-type dopants in GaAs, Mn has not due to reports for which the data has demonstrated non-uniform diffusion, low surface concentration and the degradation of GaAs surface associated with Mn diffusion. A Mn concentration of 2 $\times$ 10$\sp{18}$ cm$\sp{-3}$ was the highest reported for which a smooth GaAs surface was maintained. In addition, incorporation of Mn as a p-dopant in GaAs during MBE growth has been demonstrated to result in a low carrier concentration and a ripple-structure surface morphology most likely due to Mn segregation on the GaAs surface or a reaction with the GaAs substrate.

In this work, a study has been conducted to investigate and evaluate the effectiveness of using the various Mn-containing sources so as to diffuse Mn into GaAs, maintaining a smooth surface morphology and high doping concentration. The ampoule sealing technique has been used to perform the diffusion experiments. The various Mn-containing sources included separate solid sources of Mn, MnAs, and Mn$\sb3$As in the quartz ampoule as well as a Mn thin film deposited directly onto the substrates by electron beam evaporation. The results indicate that a very high carrier concentration as well as smooth surface can be obtained. Such depends critically on the choice of diffusion source, As overpressure, and surface encapsulation. The effect of background doping on the diffusion of Mn and a comparison of the diffusion rate of Mn with those of various p-dopant are demonstrated. The work has been further extended so as to study the optical properties of AlGaAs following Mn diffusion. In addition, the effects of Mn diffusion on both the impurity-induced layer disordering (IILD) and microstructure of undoped AlGaAs-GaAs superlattices (SLs) under various As overpressure are discussed. The interstitial-substitutional mechanism involving either Column III vacancies or the "kick-out" mechanism, depends on the surface ambient during diffusion, such has been proposed so as to explain the behavior of the Mn incorporated into GaAs and GaAs-AlGaAs heterostructures.