Group III-nitride semiconductor Schottky barrier photodiodes for radiometric use in the UV and VUV regions

We have developed Schottky barrier photodiodes of AlN, AlxGa1−xN, GaN and InyGa1−yN grown on n-SiC. Spectral responsivity measurements demonstrate that the devices fabricated have sharp cut-offs with a rejection ratio of over 3 decades and the cut-off wavelength can be varied by changing the alloy or the composition of the alloys. The internal quantum efficiency of an Al0.19Ga0.81N photodiode is estimated to reach 64% around 300 nm. It is also confirmed that the photodiodes do not notably degrade in responsivity to the UV radiant exposure of 5 kJ cm−2 in contrast to Si photodiodes. Characterization on uniformity, temperature dependence and angular response is also conducted and gives satisfactory results for all items. In conclusion, the Schottky barrier photodiodes of AlN, AlxGa1−xN, GaN and InyGa1−yN work properly as expected and look very promising for precise measurements in the VUV and UV regions.