Charge Transients by Variable Wavelength Optical Pulses in CdTe Nuclear Detectors

We study charge transients induced by optical pulses in CdTe detectors. Different carrier dynamics and collection properties are observed in the signals induced by optical excitation in the wavelength range 500-1650 nm, depending on the absorption and on the transport mechanism involved. A systematic comparison between charge transients, by irradiation through cathode and anode contacts, allows to point out the role of defects near the surface, instability effects, deep level transitions into the bulk, and internal photoelectric effects at the contacts.