Bulk resistance decay in CdTe

Bulk resistance decay of cadmium telluride (CdTe) single crystals was investigated. The bulk resistance of each CdTe single crystal was measured during long time interval. The samples were placed into a cryostat. That allowed us to hold the temperature constant during the measurements and eliminate the illumination influence. The measurements started and were continued at 300 K and after some period of time it was sharply raised up to 390 K. We observed the resistance slow decreasing with time with temperature T = 300 K and T = 390 K. All the samples have very high value of relaxation time. The presented samples must have not one but four acceptor or donor levels, some of them are deep levels. We have discovered that the interactions between the valence band and deep acceptor levels or between the conductivity band and deep donor levels cause this long value of relaxation time.