Novel silicon x-ray detector with TFT readout

Abstract

Crystalline Silicon Drift Detectors (SDDs) have been used for spectroscopy and particle physics applications since they were first reported in the 1980s[1] [2]. However, spatial resolution and a complex fabrication process are two major hurdles that prevent SDDs from seeing widespread use in diffraction imaging and protein crystallography. To overcome the issues with SDDs, we proposed a new type of silicon radiation detector integrated with a hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) readout technology intended for low X-ray energy detection with high spatial resolution [3]. This work aims to extend our previous effort by examining in detail the operation of the proposed integrated silicon TFT detector and to evaluate its X-ray sensitive performance via numerical analysis. In this research we simulate a 250-μm-thick slightly doped p-type silicon substrate that also functions as an X-ray detector integrated with a TFT readout having a channel length of 15 μm and a source/drain width of 15 μm. The simulations performed focus on the potential distribution and band structure at the heterostructure interface between the TFT and the silicon detector, and also on the current-voltage characteristics of the TFT due to X-ray exposure. Based on simulation results, the expected lower and upper limits of performance will be presented. In particular, the feasibility of a single 6 keV photon detection (arguably the minimum signal for a crystallography application) with such a device will be examined.