Research Information System
Medical Imaging 2026: Physics of Medical Imaging, Vancouver, Canada, 15 - 19 February 2025, vol.13924, (Full Text)
A novel large-area drift X-ray detector with α-Se as the photoconductor has been designed and fabricated. The structure relies on field-shaping strips emulating the well-known Frisch grid, introduced to address the low-mobility issue of heavy positive ions. An array of field-shaping strips with appropriate voltage biasing enhances the charge collection of α-Se in favor of hole, which are faster charge carrier compared to electrons in α-Se. The slower electrons and the resulting higher electron trapping probability are common issues in α-Se X-ray detectors, which degrade the energy resolution of these devices. To address the issue of slower electrons, the field-shaping strips create semi-drift electric fields within the Se bulk, isolating the collected holes from the slower electrons, which leads to enhanced charge collection and reduced signal rise time. As a result, the reduction in rise time would enhance the device's response. Moreover, holes created in the bulk of the detector would drift toward the readout electrode, further enhancing hole collection, which would lead to an increase in photocurrent response. In addition, a novel hole-blocking layer was coated on top of the α-Se to suppress the dark current, which is a major contributor to noise. Enhancing the photocurrent due to the field shaping strips and suppressing the dark current due to the hole blocking layer would result in higher SNR and improvement in energy resolution. The device was tested with blue LED, and drift strips exhibit promising results in hole collection, although X-ray tests with proper collimator are the next goals of the project for applications in X-ray imaging. As a result, low cost large area α-Se based drift detector with enhanced hole collection is achievable.