  We combined steady-state photoconductivity and laser-induced transient
current measurements under above-band-gap illumination to study the space
charge formation in CdZnTe. Analytical as well as numerical models describing
space charge limited photocurrents were developed and an excellent agreement
with measured data was obtained especially with the Drift-diffusion model.
Linear rise of photocurrent at low bias was observed and ascribed to the
trapping of injected holes at the region close to the cathode side. Influence
of space charge formation, photoconductive gain, contribution of shallow and
deep levels to photocurrent-voltage characteristics were numerically simulated.
According to the measurements and calculations, recent principles used at the
evaluation of detector properties, mainly the mobility-lifetime product, via
the photoconductivity are critically assessed.
