Improved detection of the invisible

For decades, sensing and imaging in the infrared (IR) portion of the electromagnetic spectrum has been commonplace and cost-effective, owing largely to tremendous advances in semiconductor materials and optoelectronic devices that were designed to detect light at these wavelengths. Less well known is the fact that the ultraviolet (UV) portion of the spectrum is widely used for a variety of sensing and imaging applications. However, until very recently, with the advent of wide-bandgap materials such as AlGaN, there have not been high-performance optoelectronic devices designed for optimal operation in the UV range. Thus, the development of sophisticated detection applications in the UV range has been limited by the existing technology. This article outlines recent advances in the development of high-quality UV photodetectors fabricated on GaN and AlGaN. Several specific device structures and their performance characteristics are also presented.