PhD seminar - Kyung-Wook Shin

Candidate

Kyung-Wook Shin

Title

a-Si:H-Silicon Hybrid Low Energy X-Ray Detector

Supervisor

Karim Karim

Abstract

Low energy X-ray (< 20 keV) detection is a key factor for biomedical research projects and photon counting applications. Its fast readout capability and ease of integrated circuit implementation with modern semiconductor fabrication technology enabled mass production and cost reduction for X-ray detection. On the other hand, hydrogenated amorphous silicon (a-Si:H) thin film technology enabled a huge influx of large area display products into commercial display market and active matrix flat panel imagers (AMFPIs) are replacing medical imaging equipment market with digital imagers.

Thus, in this work, we introduce a conjugated the silicon low energy detector with amorphous silicon thin film technology for large area low energy X-ray detectors. The detector was fabricated with in-house fabrication facility(G2N) utilizing plasma enhanced chemical vapor deposition (PECVD), reactive ion etching (RIE), photo-lithography, and metal sputtering technologies. Unlike most active matrix display products, top-gate staggered a-Si:H thin film transistor (TFT) was implemented to take advantage of on-site pixel amplification capability. We also developed a revised detector design with improved on/off current ratio and sensitivity with silicon dioxide (SiO2) coated silicon substrate.

The detector performance was evaluated with Iron 55 isotope source to mimic low energy X-ray exposure. We also performed noise spectrum investigation to find out the lowest detection signal level. And various tests with I-V, C-V measurement techniques indicates that the hybrid detector has a potential for low cost and large area X-ray detector (< 20 keV) applications.