Enhancement of Long-Wavelength Photoluminescence Due to Heat-Treatment in Si-Doped GaAs
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ENHANCEMENT OF LONG-WAVELENGTH PHOTOLUMINESCENCE DUE TO HEAT-TREATMENT IN Si-DOPED GaAs M. SUEZAWA. A. KASUYA. Y. NISHINA and K. SUMINO Institute for Materials ResearchTohoku University.Sendai
980.Japan
ABSTRACT Highly efficient radiative recombination even at room temperature was found at a wavelength of about 1.3 P m in heat-treated Si-doped GaAs. The range of Si concentrations and the condition of heat-treatment to yield this intense luminescence were determined. Excitation spectra of the PL lines suggest that such PL lines are related to pairs of Si-donor and Si- acceptor and such pairs combined with gallium vacancies.
INTRODUCTION The electrical and optical properties of semiconductors highly doped with impurities depend not only on the cencentration but also on the local configuration of impurity atoms in the crystal. For instance, pairs of neighboring impurity atoms having a strong interaction with the host lattice may give rise to the impurity state which is quite different from the state of a single impurity atom. The local configuration of impurity atoms is affected by thermal treatment of the crystal. A systematic study on the effect of thermal treatment on the electrical and optical properties of impuritydoped crystals may lead to the knowledge on how the local configuration of impurity atoms is developed in the crystal and, in turn, brings about specific electrical and/ or optical characteristics of the crystal. On the basis of such knowledge we may be able to find the way to control the characteristics of the crystal as we wish. This may be one of the most useful application of "Defect Engineering". Thermal treatment of a crystal induces reactions among defects and impurities which result in the formation of clusters and/or complexes having specific electronic states. In this paper we report the results of our experiment conducted from such a point of view with Si-doped GaAs. Si is an amphoteric impurity in GaAs [1]. A Si atom in a GaAs crystal works as a donor or an acceptor, depending on whether it occupies the Ga site or the As site of the crystal. An Au impurity atom in a Si crystal as a representative amphoteric impurity works as a donor when Si is p-type, and as an acceptor when n-type. Such behavior of Au impurity is related to the deep level of Au in Si. In such case, the characteristic of the level is well described with the combination of the characteristics of both conduction and valence bands. On the contrary. Si atoms in GaAs act as donors and acceptors irrespective of the conduction type of the crystal because such actions come from the difference in the occupation sites of Si atoms. The energy levels of a Si-donor and Si-acceptor are both shallow. In this point the amphoteric nature of Si in GaAs. or more generally group IV impurities in III- V compound semiconductors, is different from those of amphoteric impurities in elemental semiconductors like Si. If we are concerned with the properties nearly in thermal equilibrium, we only need to know the difference of the concentrations of
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