AlGaN-on-Si-Based 10- $\mu\hbox {m}$ Pixel-to-Pixel Pitch Hybrid Imagers for the EUV Range

We report on the fabrication of extreme ultraviolet (EUV) hybrid imagers with backside-illuminated detector chip based on aluminum gallium nitride (AlGaN) layers grown on silicon and integrated with CMOS readout chip. The focal plane array (FPA) size is 256 × 256 pixels with 10-μm pixel-to-pixel pitch. The devices were characterized at wavelengths from 300 down to 1 nm using synchrotron radiation. An upper cutoff wavelength of 280 nm was observed, as expected from the AlGaN active layer composition (40% Al). Thus, the imagers have a high rejection ratio of the near UV and visible radiation. Moreover, no degradation due to proton irradiation was observed for 60-MeV energy and 5 ·10¹⁰ protons/cm² dose. Furthermore, devices with thin silicon substrate layer that is intentionally left were fabricated, and response only in the EUV range was observed. These results demonstrate the possibility of achieving high-resolution EUV imaging with AlGaN-based FPAs, which is very promising for high-end industrial, scientific, and space applications.