Semiconductor Alloys for Operation in the Solar-Blind Region

Abstract

Researchers at the University of Central Florida have developed new cubic semiconductor alloys for UV photodetectors and light emitters for applications in covert space-to-space communications, missile threat detection, and chemical and biological threat detection.

In aerospace and defense applications, UV photodectors sense heat sources such as flames, jet engines, or missile plumes that emit light throughout the UV portion of the spectrum. By using the UCF semiconductor alloys in optoelectronic and microelectronic devices, the UV photodectors can now operate in the solar blind region allowing for faster, more reliable detection of threats or consistent communications in space.

The upper ozone layer in our atmosphere absorbs nearly 100 percent of solar radiation for wavelengths shorter than 290 nanometers, creating the spectral region termed the solar-blind region. UV detectors that operate within this solar-blind region are optimized to have sensitivity to UV-C and far UV radiation but little to no response to ground level solar spectrum providing the application-specific spectral detection. These detectors use conventional hexagonal lattice structures in semiconductor photodetectors but suffer from various problems including cracking due to strain and reduced internal quantum efficiency. In addition, difficulties often arise from the lack of a suitable lattice matched substrate, leading to higher dislocation densities. UV photodetectors and light emitters have drawn extensive attention, because of their unique capabilities of detection and ability to withstand harsh environments.

Technical Details

The UCF semiconductor material comprises a single crystal cubic oxide substrate and an epitaxial cubic oxide alloy layer consisting of a transition metal or group IIA metal on the top surface of the substrate. The material has a sodium chloride structure, in which each of the two atom types form a separate face-centered cubic lattice, with the two lattices interpenetrating to form a 3D checkerboard pattern. Since there needs to be a matching of lattice structures between two different semiconductor materials to allow a region of band gap change without introducing a change in the crystal structure, the cubic epitaxial material is lattice matched within 5 percent to the lattice of the substrate and as low as 1.5 percent.

Benefit

Market Application