Acceptor level related Shockley Read Hall centers in p-HgCdTe

Abstract We investigated the minority carrier lifetime in p-type HgCdTe layers grown using liquid-phase epitaxy and found that the lifetime was dominated by the Shockley–Read–Hall (SRH) mechanism whose recombination centers were closely associated with acceptor energy levels. We compared the lifetime and acceptor activation level in two kinds of p-HgCdTe layers having different acceptors. One kind was the conventional Hg-vacancy doped HgCdTe layers and the other kind was the Ag-impurity doped HgCdTe layers using the AgNO3 dipping solution technique. In p-type HgCdTe layers doped with Hg vacancy acceptors, the minority carrier lifetime was very short due to SRH recombination centers existing 20 meV above the valence band. This trap energy was slightly larger than that of the acceptor activation energy. When HgCdTe layers were doped with Ag, the above SRH center disappeared and the lifetime increased. In this case, the lifetime was dominated by another SRH center of 5 meV, which was again near the acceptor level of the host material. We concluded that SRH centers in Hg-vacancy doped HgCdTe layers originated from the vacancy itself and had no relationship to crystal defects. Ag replacement seems to have brought about the only energy state change for vacancy-related SRH centers where the energy shift corresponded to the acceptor level shift.