Industries such as the automotive, aerospace or military, as well as environmental and biological research have promoted the development of ultraviolet (UV) photodetectors capable of operating at high temperatures and in hostile environments. UV-enhanced Si photodiodes are hence giving way to a new generation of UV detectors fabricated from wide-bandgap semiconductors, such as SiC, diamond, III-nitrides, ZnS, ZnO, or ZnSe. This paper provides a general review of latest progresses in wide-bandgap semiconductor photodetectors.

https://iopscience.iop.org/article/10.1088/0268-1242/18/4/201/pdf

Wide-bandgap semiconductor ultraviolet photodetectors

III nitrides have become the most exciting challenge in optoelectronic materials in the last decade. Their intrinsic properties and an intense technological effort have made possible the fabrication of reliable and versatile detectors for short wavelengths. In this work, materials and devices issues are considered to provide a full picture of the advances in nitride UV photodetection. First, basic structures like photoconductors, Schottky, p-i-n and metal-semiconductor-metal photodiodes and phototransistors are compared, with emphasis on their specific properties and performance limitations. The efforts in the design and fabrication of more advanced detectors, in the search for higher quantum efficiency, contrast, signal-to-noise or speed operation, are reviewed afterwards. Metal-insulator-semiconductor diodes, avalanche photodetectors and GaN array detectors for UV imaging are also described. Further device optimization is linked with present materials issues, mainly due to the nitride quality, which is a direct result of the substrate used. The influence of substrates and dislocations on detector behaviour is discussed in detail. As an example of AlGaN photodetector applications, monitoring of the solar UV-B radiation to prevent erythema and skin cancer is presented.

https://iopscience.iop.org/article/10.1088/0953-8984/13/32/316/pdf

III nitrides and UV detection

The development of high-performance optical receivers has been a primary driving force for research on III-V compound avalanche photodiodes (APDs). The evolution of fiber optic systems toward higher bit rates has pushed APD performance toward higher bandwidths, lower noise, and higher gain-bandwidth products. Utilizing thin multiplication regions has reduced the excess noise. Further noise reduction has been demonstrated by incorporating new materials and impact ionization engineering with beneficially designed heterostructures. High gain-bandwidth products have been achieved waveguide structures. Recently, imaging and sensing applications have spurred interest in low noise APDs in the infrared and the UV as well as large area APDs and arrays. This paper reviews some of the recent progress in APD technology.

Recent advances in avalanche photodiodes

AlGaN-based UV photodetectors

This paper will review recent advances in linear- and Geiger mode avalanche photodiodes (APDs). The focus for linear-mode devices will be materials and structural modifications to the conventional InP/InGaAs APD that have enabled reduced excess noise and enhanced gain-bandwidth products. The discussion of Geiger mode APDs will cover the basic operation and principal performance parameters with emphasis on techniques to reduce afterpulsing.

Avalanche photodiodes have been demonstrated utilizing GaN grown by hydride vapor-phase epitaxy. Spatially uniform gain regions were achieved in devices fabricated on low-defect-density GaN layers that exhibit no microplasma behavior. A uniform multiplication gain up to 10 has been measured in the 320–360 nm wavelength range. The external quantum efficiency at unity gain is measured to be 35%. The electric field in the avalanche region has been determined from high-voltage C–V measurements to be ∼1.6 MV/cm at the onset of the multiplication gain. Electric fields as high as 4 MV/cm have been measured in these devices. Response times are found to be less than 5 μs, limited by the measurement system.

S. S. Choi

Papers

GaN avalanche photodiodes grown by hydride vapor-phase epitaxy