Abstract: The invention provides a device having a substrate, a buffer region positioned upon the substrate, wherein the buffer region has an upper buffer region and a lower buffer region, a heterojunction region positioned upon the buffer region, and a superlattice positioned between the lower buffer region and the upper buffer region, wherein the device is configured to function as a heterojunction field effect transistor.

Abstract: Photodetectors are constructed with ternary semiconductor alloys, for which the band gap varies with composition, to fabricate a photodetector and optical filter combination. The detectors are part of a measuring system that measures, stores and displays UV intensity versus time, peak intensity, total UV energy and temperature. It simultaneously measures a plurality of different UV ranges and temperatures. The output of the sensing system is converted to digital form and displayed on a visually perceptible device. Preferably total UV dosage and peak intensity are displayed for each monitored UV band, together with the maximum temperature. By manufacturing the photodetectors and filters with a ternary semiconductor alloy, sensors can be constructed which have a photoresponse to light in a narrow wavelength band and are blind to light outside of the wavelength band. Each sensor includes a filter and photodetector section, each of which includes ternary semiconductor alloys (i.e.