SOI detector with drift field due to majority carrier flow — An alternative to biasing in depletion

This paper reports on a SOI detector with drift field induced by the flow of majority carriers. It is proposed as an alternative method of detector biasing compared to standard depletion. N-drift rings in n-substrate are used at the front side of the detector to provide charge collecting field in depth as well as to improve the lateral charge collection. The concept was verified on a 2.5 ×2.5mm² large detector array with 20 μm and 40 μm pixel pitch fabricated in August 2009 using the OKI semiconductor process. First results, obtained with a radioactive source to demonstrate spatial resolution and spectroscopic performance of the detector for the two different pixel sizes, will be shown and compared to results obtained with a standard depletion scheme. Two different diode designs, one using a standard p-implantation and one surrounded by an additional BPW implant will be compared as well.