Pixelized M-π-n CdTe detector coupled to Medipix2 readout chip

Abstract

We have realized a simple method for patterning an M-π-n CdTe diode with a deeply diffused pn-junction, such as indium anode on CdTe. The method relies on removing the semiconductor material on the anode-side of the diode until the physical junction has been reached. The pixelization of the p-type CdTe diode with an indium anode has been demonstrated by patterning perpendicular trenches with a high precision diamond blade and pulsed laser. Pixelization or microstrip pattering can be done on both sides of the diode, also on the cathode-side to realize double sided detector configuration. The article compares the patterning quality of the diamond blade process, pulsed pico-second and femto-second lasers processes. Leakage currents and inter-strip resistance have been measured and are used as the basis of the comparison. Secondary ion mass spectrometry (SIMS) characterization has been done for a diode to define the pn-junction depth and to see the effect of the thermal loads of the flip-chip bonding process. The anode and cathode-sides of a 6 × 6 mm 2 diodes were patterned with a diamond blade and flip-chip bonded to the Medipix2 readout chips. First imaging results with an X-ray source show reduced polarization effect and edgeless detector behavior for the anode-side patterned detector.

Characterization of M-π-n CdTe pixel detectors coupled to HEXITEC readout chip

“…As an alternative, the manufacturers use aluminium to form the blocking contact due to its improved stability, however, it suffers from poorer leakage current performance in comparison to indium contacts. If the pixellated indium anode is instead segmented using a diamond blade [1,2], where a physical cut through the indium diffused layer is used to pattern the electrode, then good inter-pixel isolation can be achieved.…”

“…Authors have previously reported [1], a simple method to pattern the anode-side of M-π-n CdTe detectors. Electrical characterization results of segmented M-π-n CdTe diodes with different patterning methods have also been reported [2]. It was shown that low leakage currents and high inter-strip resistances are obtained with both diamond blade and pulsed laser patterning methods.…”

Characterization of Edgeless CdTe Detectors for use in Hard X-Ray Imaging Applications

“…CdTe diode detectors were used in this study due to their excellent energy and leakage current performance [8], [9], [12]. The CdTe diode detectors, typically, have an indium anode that forms a Schottky contact on the CdTe while the cathode is produced from gold or platinum giving an Ohmic contact.…”

“…0018-9499/$31.00 © 2012 IEEE Rather than use standard photolithography, it is possible to segment the indium anode using a diamond blade. In this technique a physical cut through the indium diffused layer is used to pattern the electrode [8], [9]. This produces detectors with excellent leakage current performance, high inter-pixel resistance and an active area that extends to the detector edges.…”