Cancellation method to improve signal to noise ratio of an electrodeless microwave-biased ZnO single crystal x-ray detector.

Abstract

Semiconductor x-ray detectors are usually fabricated with proper ohmic or Schottky contact electrodes, which make the fabrication process complex and even unable to realize, especially for new materials. In this paper, we demonstrated an electrodeless ZnO single crystal x-ray detector using microwave (MW) bias with a high signal-to-noise ratio obtained by a cancellation method. The MW-biased x-ray detector is fabricated using the split-ring-resonator with the ZnO crystal mounted on the split-ring gap. The analytical response model was built for the detector. The MW cancellation process was realized by a phase and amplitude matching network. By using the cancellation method, the signal-to-noise ratio of the detector is about 59.4 dB, which is 58 dB higher than that of the DC-biased ZnO photodetector. The sensitivity of the detector is 139 µC Gy-1cm-2 for the x-ray dose rate of 3.54 Gy/s, which is 86 times higher than that of the DC-biased ZnO photodetector. The high sensitivity of the detector is due to the high equivalent stimulated voltage caused by the split-ring resonator. The MW-biased detector can be used for x-ray dose monitoring.