Temperature dependent characterization of gallium arsenide X-ray mesa p-i-n photodiodes

Electrical characterization of two GaAs p(+)-i-n(+) mesa X-ray photodiodes over the temperature range 0 degrees C to 120 degrees C together with characterization of one of the diodes as an X-ray detector over the temperature range 0 degrees C to 60 degrees C is reported as part of the development of photon counting X-ray spectroscopic systems for harsh environments. The randomly selected diodes were fully etched and unpassivated. The diodes were 200 mu m in diameter and had 7 mu m thick i layers. The leakage current density was found to increase from (361) nA/cm(-2) at 0 degrees C to (24.36+/-0.05) mu A/cm(-2) at 120 degrees C for D1 and from a current density smaller than the uncertainty (0.2+/-1.2) nA/cm(-2) at 0 degrees C to (9.39+/-0.02) mu A/cm(-2) at 120 degrees C for D2 at the maximum investigated reverse bias (15 V). The best energy resolution (FWHM at 5.9 keV) was achieved at 5V reverse bias, at each temperature; 730 eV at 0 degrees C, 750 eV at 20 degrees C, 770 eV at 40 degrees C, and 840 eV at 60 degrees C. It was found that the parallel white noise was the main source of the photopeak broadening only when the detector operated at 60 degrees C, at 5V, 10V, and 15V reverse bias and at long shaping times (>5 mu s), whereas the sum of the dielectric noise and charge trapping noise was the dominant source of noise for all the other spectra. (C) 2016 AIP Publishing LLC.