GaN UV detectors for synchrotron-based protein structure studies

AlGaN and GaN have been investigated as UV detector materials for applications in protein structure studies. I-V characteristics performed on the material using concentric contacts showed 4 orders of magnitude of greater dark current for the Al0.1Ga0.9N than for the GaN. Subsequently, interdigitated metal-semiconductor-metal (MSM) photodetectors were successfully fabricated on GaN. No changes in levels of dark surrent were recorded using varying metal electrodes with similar work functions (Pd and Au). The unbiased diodes showed a difference of 3 orders of magnitude between dark and photocurrent levels on exposure to UV. The responsivity for diodes with 25 and 100μm finger separation operated in unbiased mode was around 100 mA/W and was flat over the bandgap. These results show a responsivity in agreement with those from previous measurements for biased GaN photodetectors [Phys. Stat. Solid: 176 (1999) 157]. Using these results, a design for an unbiased GaN detector to be used for protein structure studies is proposed.