CDTE IN PHOTOCONDUCTIVE APPLICATIONS FAST DETECTOR FOR METROLOGY AND X-RAY-IMAGING

Operating as a photoconductor, the sensitivity and the impulse response of semi-insulating materials greatly depend on the excitation duration compared to electron and hole lifetimes. The requirement of ohmic contact is shortly discussed. Before developing picosecond measurements with an integrated autocorrelation system, this paper explains high energy industrial tomographic applications with large CdTe detectors (25 x 15 x 0.9 mm3). The excitation is typically in the mus range. X-ray flash radiography, with a 10 ns burst, is in an intermediate time domain where the excitation is similar to the electron lifetime. In laser fusion experiments excitation is in the 50 ps range and we develop photoconductive devices able to study very high speed X-ray emission time behaviour. Thin polycrystalline MOCVD CdTe films with picosecond response are suitable to perform optical correlation measurements of single shot pulses with a very large bandwidth (approximately 50 GHz).