Position-Sensitive Avalanche Photodiodes for Gamma-Ray Imaging

In this paper, we report on the investigation of silicon avalanche photodiodes (APDs) for high-energy photon imaging applications. This includes a new APD design that provides X-ray and -ray imaging with significant reduction in electronic readout requirements. This new APD design, referred to as position-sensitive avalanche photodiode (PSAPD), involves charge sharing amongst the electrodes that enable determination of position of interaction. PSAPDs with 14 14 mm area have been fabricated using planar processing. The performance of these devices has been evaluated for energy resolution, timing resolution (4 ns full-width at half-maximum), and spatial resolution ( 300 m intrinsic spatial resolution). The potential of these APDs in high-energy physics and medical imaging is addressed.