Current noise spectra in CdTe semiconductor diodes

By using a correlation spectrum analyzer, we succeeded in performing direct measurements of the current noise spectra of cadmium telluride (CdTe) diod es, commonly used in gamma-ray spectrometers. The current noise spectra hav e been measured over a wide range of frequencies, from below 1 Hz up to 100 kHz, and for diode operating points from 0 up to 150 V. The device showed linear I-V characteristics in all the bias range with a dynamic resistance of about 2 G Omega. Around the equilibrium condition (0-0.5 V), the white c omponent of the noise spectrum is in agreement with the Johnson noise assoc iated to the device resistance. As the bias is increased up to 150 V, the w hite noise level is shown to slowly approach the shot noise behavior. The w hite noise shows a cut-off frequency consistent with the carriers transit t ime across the device. In all the nonequilibrium conditions, the noise spec tra also show a significant 1/f component whose power density increases wit h the square of the device current. (C) 2000 American Institute of Physics. [S0021-8979(00)00110-9].