GaN-Based Low-Energy X-Ray Single Photon Detector With Photon Energy Resolution and Fast Response

This work presents the demonstration of a GaN based low-energy X-ray single photon detector with photon energy resolution capability. By adopting the GaN-on-GaN high quality epitaxy technique, slant mesa termination structure, and well-modified ohmic contact layer, a fully vertical GaN p-i-n diode with leakage in pA level and low parasitic resistance has been fabricated, achieving a low-energy X-ray photon detector with extremely low noise figure below $1\times 10^{-{28}}\,\,\text{A}^{2}$ /Hz and fast response within $1.0~\mu \text{s}$ . With a specifically established reset charge sensitive amplification circuit, superior linearity has been obtained between the output Gaussian peak position and the photon energy in the investigated range of approximately 10 keV to 20 keV, enabling the photon energy resolution with a high carrier collection ratio. This work thus validates the merits of GaN in low-energy X-ray detection, providing a promising solution with high temperature stability and radiation hardness.