Radiation detection measurements with a new "Buried Junction" silicon avalanche photodiode

An improved version of a recently developed "Buried Junction" avalanche pho todiode (APD), designed for use with scintillators. is described and charac terized. This device. also called the "Reverse APD", is designed to have a wide depletion layer and thus low capacitance, but to have high gain only f or e-h pairs generated within the first few microns of the depletion layer. Thus it has high gain for light from scintillators emitting in the 400 600 nm range, with relatively low dark current noise and it is relatively inse nsitive to minimum ionizing particles (MIPs). An additional feature is that the metallurgical junction is at the back of the wafer, leaving the front surface free to be coupled to a scintillator without fear of junction conta mination. The modifications made in this device, as compared with the earli er diode, have resulted in a lower excess noise factor, lower dark current, and much-reduced trapping. The electrical and optical characteristics of t his device are described and measurements of energy and timing resolution o f this device with several scintillators (BGO, LSO and GSO) of potential in terest in high-energy physics and PET imaging systems are presented. (C) 19 99 Elsevier Science B.V. All rights reserved.