AlGaN-Based Self-Powered Solar-Blind UV Focal Plane Array Imaging Photosensors: Material Growth, Device Preparation, and Functional Verification

This article reports the development of hybrid AlGaN-based self-powered solar-blind ultraviolet (UV) focal plane array (FPA) imaging photosensors from material growth and array preparation to functional verification. The detailed process starts with the epitaxial growth by metal-organic chemical vapor deposition (MOCVD). A high-quality AlN template is obtained on the 2-in double-polished c-plane sapphire substrate by introducing a mesothermal AlN (MT-AlN) interlayer and adjusting the growth rate of the high-temperature AlN epilayer (HT-AlN). Then, a polarization-enhanced p-i-n structure photodetector material is grown on the AlN template. Subsequently, based on the p-i-n structural material, a 320 x 256 back-illuminated solar-blind photodiode array is fabricated and hybridized to a matching Si-based CMOS readout integrated circuit (ROIC) chip to form a focal plane detector. Solar-blind UV detection is observed throughout the array in the 262-281-nm spectral region with a peak external quantum efficiency (EQE) of 65.3% at zero-bias voltage (no antireflection coating) and a nanosecond transient response time at a reverse bias of 5 V. The visible response of the ROIC is eliminated by developing a masking technology that is opaque to visible light, which enables the focal plane detector to achieve a high UV/visible rejection ratio of more than 10(4).