  Bridgman CdTe and CdZnTe crystal growth, with cadmium vapor pressure control,
is applied to production of semiconductor gamma radiation detectors. Crystals
are highly donor doped and highly electrically conducting. Annealing in
tellurium vapors transforms them into a highly compensated state of high
electrical resistance and high sensitivity to gamma radiation. N-type
detectors, equipped with ohmic contacts, and a grounded guard ring around the
positive contact, are not sensitive to hole trapping. Conductivity control, by
the doping level, optimizes the detector operation by trade-off between
electrons' lifetime and electrical resistance. Gamma spectra of single
detectors and detector arrays are presented. Detector optimization and gamma
detection mechanisms are discussed.
