Characterization of charge collection in CdTe and CZT using the transient current technique

Abstract The charge collection properties of Cadmium–Telluride (CdTe) and Cadmium–Zinc–Telluride (CZT) in comparison with Silicon (Si) are presented using the transient-current technique (TCT) where the current pulses are generated by α -particles emitted from an 241 Am source. From the recorded current pulse shapes, the charge collection efficiency, the charge carrier mobility and the electric field distribution inside the detectors are extracted. In particular, the signals of the compound semiconductors CdTe and CZT are interpreted with respect to the build-up of space–charges in the sensor volume and the subsequent deformation of the electric field. As high-quality CdTe and CZT samples are now commercially available, the knowledge of these material characteristics is of outmost importance for the application of CdTe and CZT in X-ray imaging. In addition, the paper describes the influence of Ohmic and Schottky contacts on the current pulses in CdTe as well as the effects of polarization, i.e. the time-dependent degradation of the detector signals due to the accumulation of fixed charges within the sensor.

[1]  O. Krasel Charge collection in irradiated silicon detectors , 2004 .

[2]  J. Mayer,et al.  Observation of Double Injection in Long Silicon p-i-n Structures , 1965 .

[3]  K. Zanio,et al.  Transient Currents in Semi‐Insulating CdTe Characteristic of Deep Traps , 1968 .

[4]  W. Shockley Currents to Conductors Induced by a Moving Point Charge , 1938 .

[5]  A. Taroni,et al.  PLASMA TIME AND RELATED DELAY EFFECTS IN SOLID STATE DETECTORS. , 1969 .

[6]  P. Siffert,et al.  Polarization in Cadmium Telluride Nuclear Radiation Detectors , 1976, IEEE Transactions on Nuclear Science.

[7]  Tadayuki Takahashi,et al.  High resolution Schottky CdTe diode detector , 2001 .

[8]  Paul Siffert,et al.  Internal field distribution in CdTe detectors prepared from semi-insulating materials , 1994, Optics & Photonics.

[9]  P. Tove,et al.  Charge collection in silicon detectors for strongly ionizing particles , 1973 .

[10]  I. Kanno A model of charge collection in a silicon surface barrier detector , 1990 .

[11]  C. Canali,et al.  Transport Properties of CdTe , 1971 .

[12]  William Trischuk,et al.  Charge-carrier properties in synthetic single-crystal diamond measured with the transient-current technique , 2005 .

[13]  R. Klingenberg,et al.  Measurement of trapping time constants in proton-irradiated silicon pad detectors , 2003, 2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515).

[14]  K. Kao Double injection in solids with non-ohmic contacts. I. Solids without defects , 1984 .

[15]  W. Galster,et al.  The influence of plasma effects on the timing properties of surface-barrier detectors for heavy ions , 1985 .

[16]  I. Turkevych,et al.  High-temperature electron and hole mobility in CdTe , 2002 .

[17]  Milko Jakšić,et al.  Investigation on the electric field profile in CdTe by ion beam induced current , 1996 .

[18]  G. Entine,et al.  Time-dependent polarization of CdTe gamma-ray detectors , 1974 .

[19]  S. Ramo Currents Induced by Electron Motion , 1939, Proceedings of the IRE.

[20]  C. Jacoboni,et al.  A review of some charge transport properties of silicon , 1977 .

[21]  Kazuyuki Hirose,et al.  High-resolution Schottky CdTe diode for hard X-ray and gamma-ray astronomy , 1999 .

[22]  F. Goulding,et al.  Semiconductor Radiation Detectors , 1970, Science.