Arsenic incorporation in MBE‐grown HgCdTe studied with the use of ion milling

Abstract

Ion milling was employed for the study of arsenic incorporation in molecular beam epitaxy‐grown Hg0.8Cd0.2Te films doped in situ. The behaviour of specific defects, which formed after injection of mercury interstitials provided by the milling, allowed for estimating density of electrically active arsenic atoms. It is confirmed that the most efficient incorporation of As occurs when arsenic flux cracking is used, at the cracking zone temperature Tcr > 700 °C. Growth with doping without cracking was found to be accompanied by formation of Te‐related defects, which ion milling activated electrically. Films doped from the cracker cell with Tcr > 700 °C appear to be almost free of these defects. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrical properties of HgCdTe films grown by MOCVD and doped with as

“…Interestingly, however, in samples 1 and 3 the electron mobility extracted with DMSA right after the milling appeared to be higher than that in the as−grown samples. This contrasts these films to other MCT samples studied earlier [10,11,16,19,20], and could be explained by partial de−compensation of the film occurring via Hg vacancy filling and formation of donor complexes comprising As atoms, as described below, along with the relatively low total concentration of donor complexes right after ion milling.…”

“…The measurements performed on the samples which were subjected to a number of steps of chemical etch− ing, showed that these values of donor concentration per− sisted throughout the whole film. Such values of residual donor concentration are typical of MCT films grown on GaAs substrates by MBE [10,11], and of MOCVD films grown with the other technology [20].…”

“…Also, relaxation data are shown for a nominally un−doped n−type MBE film grown on a GaAs substrate, and a vacancy−doped p−type MBE film grown on a Si substrate. Details on the fabrication of the ISOVPE and MBE films and on the study of their properties with the use of ion mill− ing were given elsewhere [10,11,16,19,20]. Straight after the milling the mobility of the electrons μ n was quite low for the given x values.…”

“…After the complete relaxation (t~100000 min) the mobility in the MOCVD films remained quite low, which showed that though the compensation degree was reduced, there was still a considerable number of scattering centres present. Those could be either acceptors, which do not interact with Hg I during the milling, or some structural defects [20]. Usually, the mobility after the relaxation is higher than that in as−grown films, as ion milling reduces the degree of compensation [10,11].…”

Evolution of MBE HgCdTe defect structure studied with ion milling method

“…It appears, that strongly non-equilibrium processes which take place under IM, when material is oversaturated with interstitial mercury atoms Hg I generated near the surface [1][2], lead to the appearance of specific defect complexes, which may not form under other conditions. These complexes may also comprise intrinsic point and extended defects that normally do not show their presence due to their electrical neutrality or compensation [4,10].…”