Optimal design of the charge layer doping concentration and thickness of InP/InGaAs SPAD detectors

Abstract

The performance of InP/InGaAs SPAD detectors depends on the electrical field distribution in their multiple layers. In the conventional separate absorption, grading, charge and multiplication (SAGCM) structure, the major function of the charge layer is to confine the electrical fields, so the charge layer’s parameter design is very important for any enhanced SPAD detectors. Normally the sheet density equals to doping concentration times thickness is considered as one of the key factors for the device design, however, even with the same sheet density, there are different combinations of doping densities and thicknesses. Our calculations show that with the same sheet density of charge layer, the one with higher doping concentration has higher electrical fields in both multiplication and absorption layers, then has lower breakdown and punch-through voltages. The results were also verified by the experimental measurements.