Segmentation of the anode-side of an M-π-n CdTe diode, where the pn-junction is diffused into the detector bulk, produces large improvements in the spatial and energy resolution of CdTe pixel detectors. It has been shown that this fabrication technique produces very high interpixel resistance and low leakage currents are obtained by physical isolation of the pixels of M-π-n CdTe detectors. In this paper the results from M-π-n CdTe detectors stud bonded to a spectroscopic readout ASIC are reported. The CdTe pixel detectors have 250 µm pitch and an area of 5 × 5 mm 2 with thicknesses of 1 and 2 mm. The polarization and energy resolution dependence of the M-π-n CdTe detectors as a function of detector thickness are discussed. KEYWORDS: Solid state detectors; X-ray detectors; Detector control systems (detector and experiment monitoring and slow-control systems, architecture, hardware, algorithms, databases); X-ray radiography and digital radiography (DR)
Segmentation of the anode-side of a CdTe diode produces detectors with excellent spatial and energy resolution while maintaining an active area that extends to the detector edge. The CdTe pixel detectors reported have 250 ìm pitch, a detector thicknesses of 1 mm and are bonded to a spectroscopic readout ASIC. The results from an edgeless CdTe detector with indium-diffused anodes, produced via diamond blade segmentation, are compared to those of a CdTe Schottky pixel detector with aluminium anodes and guard band produced using standard photolithographic techniques. The energy resolution at 59.54 keV was measured to be 1.4% and 1.3% for the standard and edgeless detector respectively. The spectroscopic performance of pixels located at the detector edges are discussed with reference to TCAD simulations and X-ray micro-beam measurements.
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.
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