I(t), I(V) and surface effects studies of vapor grown and solution grown HgI2 detectors

The experiments we have carried out during the last years show that solution grown HgI2 crystals exhibit a lower μτ product than vapor grown crystal, despite a crystalline perfection and a purity at least as high, or even higher. They also show different surface properties. From the current response I(t) following a voltage step, and from the I(V) characteristic analysis, we determine the trapping levels Et present in the sample and show the influence of the contact deposition technique and surface treatments on the electrical field gradient nearby the electrode. A nitric acid treatment increases the blocking effect of the cathode contact on solution grown crystal, and therefore improves their detection performance for low energy X-rays and gamma rays. (orig.)