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?°C to 120?°C together with characterization of one of the diodes as an X-ray detector over the temperature range 0?°C to 60?°C is reported as part of the development of photon counting X-rayspectroscopic systems for harsh environments. The randomly selected diodes were fully etched and unpassivated. The diodes were 200?µm in diameter and had 7?µm thick i layers. The leakage current density was found to increase from (3?±?1)?nA/cm-2 at 0?°C to (24.36?±?0.05)?µA/cm-2 at 120?°C for D1 and from a current density smaller than the uncertainty (0.2?±?1.2)?nA/cm-2 at 0?°C to (9.39?±?0.02)?µA/cm-2 at 120?°C for D2 at the maximum investigated reverse bias (15?V). The best energy resolution (FWHM at 5.9?keV) was achieved at 5?V reverse bias, at each temperature; 730?eV at 0?°C, 750?eV at 20?°C, 770?eV at 40?°C, and 840?eV at 60?°C. It was found that the parallel white noise was the main source of the photopeak broadening only when the detector operated at 60?°C, at 5?V, 10?V, and 15?V reverse bias and at long shaping times (>5?µs), whereas the sum of the dielectricnoise and charge trapping noise was the dominant source of noise for all the other spectra.