Performance of a junction termination extension avalanche photodiode for use with scintillators

Abstract

Abstract. An avalanche photodiode with a ring structure called junction termination extension (JTE) was built and tested. It has three diffused rings around the main junction to avoid early breakdown at the surface. The JTE rings have less doping than the main junction and can be built by well controlled single ion-implantation through a single mask. Avalanche photodiodes with two mm diameter active area have been have been built by implantation of boron with a dose of 2, 3, 4 and 5 x 10 12 cm -2 , followed by deep diffusion of the junction up to 14 µm. The dark current is strongly dependent on the implantation dose, decreasing with decreasing charge. For the APDs with implanted dose of 5 x 10 12 cm -2 a gain of 8 is obtained at 1120 V. The energy resolution from a 137 Cs source was measured to be 24.4% FWHM with a 2 x 2 x 2 mm3 BGO scintillator. We have also performed simulations of the gain and breakdown voltage that correlate well with the results.