Measurement of Electron Diffusion Length by Photoluminescence in p-Doped GaAs Substrates and p-Doped Epitaxially Grown GaAs Photocathodes

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This chapter discusses measurement of electron diffusion length by photoluminescence in p-doped GaAs substrates and p-doped epitaxially grown GaAs photocathodes. The knowledge of the diffusion length of electrons in p-doped GaAs photocathodes is of paramount importance in determining the yield of such cathodes. In this study, three aspects of the problem were investigated. Photocathodes were grown epitaxially on various single-crystal GaAs substrates with heavy Zn doping. Several substrates were studied with different surface preparations and their photoluminescence characteristics were compared. Several epitaxially grown films, with different characteristics, were measured while these films were still on the substrate. The effects of the photocathode activation process on these films were studied by measuring photoluminescence before activation and after several activation cycles during which the samples were exposed to high-temperature heat treatment. Luminescent intensities varied over a wide range and other features of the spectra such as half width, band shape, and peak position displayed considerable variations as well. The qualitative conclusion that is drawn from this study is that both intensity and half width increase with increasing doping. This is supported by theory as well, although the relations are a little more involved regarding the half width. © 1972, Academic Press Inc. (London) Ltd.

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Advances in Electronics and Electron Physics