The reduction of the leakage current of radiation detectors by a simple cap implantation process

The depletion layer of PN junction of semiconductor radiation detectors usually spreads and reaches to the back side of the wafer while it spreads laterally to a distance comparable to the thickness of the wafer during operation. The area of the lateral spreading has a large fraction relative to the core active region, and an extra guard ring structure is difficult to adopted for some imaging detector array such as "Edge On" stripe detectors. Because there is a great deal of interface states and much higher density of defects at the SiO₂-Si interface than that in the bulk, surface leakage current arises from the lateral spreading of the depletion layer. We demonstrate in this report that a simple cap implantation at the surface of a radiation stripe detector can effectively reduce the surface leakage current.