Effects of Electron Radiation on the Electrical and Optical Properties of HgCdTe

An 80° K 5-MeV electron irradiation of n-type Hg1-xCdxTe produced an increase in donor density, Hall mobility, and apparent bandgap, Prior to irradiation, the donor density was 2.6 × 1014 cm-3 and increased linearly with electron fluence, with an introduction rate (dn/dΦ) of 5.7 cm-1. The 80° K preirradiation Hall mobility of 5.78 × 104 cm2/V-sec initially increased with irradiation, saturating at a value of about 1.1 × 105 cm2/V-sec for Φ = 4 × 1014 e/cm2. The irradiation-induced changes in the Hall mobility and donor density show a nearly complete recovery to their preirradiation values during isochronal anneals to 340° K. An apparent shift in bandgap to higher energy of ~0.035 eV was noted in photoconductivity data following irradiation and partial anneal. This shift in bandgap disappears during anneal, and results in a bandgap value slightly smaller than the preirradiation value after annealing to 340°K. Arguments are given to correlate the apparent bandgap increase and possibly the increased 80°K Hall mobility that is observed after irradiation and prior to anneal, with the onset of degeneracy as the carrier density increases with irradiation.