Extrinsic p-doped HgCdTe grown by direct alloy growth organometallic epitaxy

Abstract

This paper describes the doping behavior of arsenic in HgCdTe, grown by organometallic epitaxy using the direct alloy growth process. It is shown that arsenic readily incorporates into HgCdTe during this growth process, to a doping concentration of 1×1017 cm−3. Secondary-ion mass spectroscopy (SIMS) data clearly establishes the presence of arsenic in these layers. Moreover, excellent stability under annealing conditions (16 h at 270 °C followed by 10 h at 220 °C) indicates the suitability of arsenic as an extrinsic dopant source for HgCdTe. The net acceptor concentration is shown to be linearly proportional to the Hg overpressure. This fact, combined with mobility values which are comparable to those of bulk grown material, indicates that these layers are relatively uncompensated. High mobility values are preserved well into the saturated region of the acceptor concentration versus arsine flow rate characteristic. This is explained by the fact that the doping concentration is limited by surface coverage of the As species, and not by arsenic incorporation into compensating or inactive sites. Evidence for this process is presented by the SIMS data, which shows that the total arsenic concentration is linearly related to the net acceptor concentration over the entire doping range.