INVESTIGATION ON THE ELECTRIC-FIELD PROFILE IN CDTE BY ION-BEAM-INDUCED CURRENT

The charge collection efficiency profile along the thickness of a CdTe detector was measured for first time by using a proton microbeam and a polished cross-section of the devices. Different samples were invest igated and tests were carried out along different lines from cathode t o anode, with different biases and polarities, and with different shap ing times. The effects of all these parameters are evident in the expe rimental curves. By fitting these curves, the behaviour of the drift l ength for electrons and holes is obtained, if a constant ratio between them is assumed. If the mobilities and trapping times are uniform, th e electric field profile is obtained. The profile has a minimum at the anode and a maximum towards the cathode, at least for large bias volt age.