The growth and properties of In-doped metalorganic vapor phase epitaxy interdiffused multilayer process (HgCd)Te

Abstract

Indium doping of Hg1−xCdxTe layers grown by metalorganic vapor phase epitaxy using the interdiffused multilayer process has been investigated using trimethyl indium as the dopant source. The epitaxial growth was performed onto 2° off 〈100〉 CdTeSe substrates at ∼350 °C using dimethyl cadmium (DMCd) and di-isopropyl telluride as the alkyl sources. Doping in the range 1017–2×1018 cm−3 was achieved. By comparing Hall effect measurements of carrier concentration with secondary ion mass spectrometry analyses of the In concentrations in the layers, it was found that the In was only 30% active in the as-grown layers but ∼100% active after Hg-rich isothermal annealing at 250 °C for 48 h. At In concentrations greater than 2×1018 cm−3, the carrier concentration levels off, probably due to the solubility limit of In being reached. The annealed doped layers show slightly higher carrier mobilities than as-grown layers for the same carrier concentration. An apparent shift of the absorption edge to shorter wavelength with increasing donor concentration is thought to be due to the Moss–Burstein effect rather than a change in alloy composition x. A significant ‘‘memory’’ effect has been found with trimethyl In which persists for several runs and is probably due to strong adsorption onto the stainless steel surfaces in the growth system. This can be overcome by vacuum baking of the pipework. The growth of a heterostructure using In doping has shown that there is no serious diffusion problem with In under the growth conditions used.