The spectral resolution of high temperature GaAs photon counting soft X-ray photodiodes

High temperature GaAs X-ray detectors

“…The thicker i layer of the presently reported devices, compared to previously reported thinner GaAs p þ -i-n þ mesa photodiodes, [15][16][17][18] resulted in higher quantum detection efficiency and improved energy resolution at the investigated temperature range. The improved energy resolution of the presently reported spectrometer was attributed to the reduced white series, 1/f, and dielectric noise, all depending upon the capacitance of the photodiode.…”

“…Although the spectrometers S1 and S2, employing the diodes, D1 and D2, respectively, had better energy resolution (FWHM at 5.9 keV) compared to previously reported thinner GaAs p þ -i-n þ mesa X-ray photodiodes, [15][16][17][18] further work is required to improve the FWHM to values close to the best results achieved with planar Schottky contact GaAs X-ray detectors at room temperature; 0.266 keV FWHM at 5.9 keV 12 and 0.300 keV FWHM at 5.9 keV. 14 Thicker devices would result in a lower capacitance, which has a direct effect in reducing the white series, 1/f, and dielectric noises.…”

“…Work has also been conducted on GaAs p þ -i-n þ mesa X-ray photodiodes with increasing i layer thickness. The energy resolution of GaAs p þ -i-n þ mesa X-ray photodiodes with 2 lm thick i layers was investigated as a function of temperature; it was found to broaden from 0.8 keV at room temperature to 1.5 keV at 80 C. 15 GaAs p þ -i-n þ mesa X-ray photodiodes with 3 lm i layer thickness were studied at 33 C over the energy range 4.95 keV to 59.5 keV; the energy resolution (FWHM) was found to range from 0.78 keV to 0.95 keV for a 200 lm diameter device and from 1.08 keV to 1.33 keV for a 400 lm diameter device. 16 Systematic study of fabrication techniques for GaAs p þ -i-n þ mesa X-ray photodiodes with 7 lm i layer thickness investigated the effects of wet chemical etchants and etch depths on the dark currents of such devices; a fully etched 400 lm diameter diode had a FWHM at 5.9 keV of 1 keV, at room temperature.…”

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

“…The best energy resolution (FWHM at 5.9 keV) was achieved at 5 V reverse bias at each investigated temperature. It was measured to be 730 eV at 0 C, 750 eV at 20 C, 770 eV at 40 C, and 840 eV at 60 C. The other previously reported that 7 lm GaAs devices had an energy resolution of $1 keV at room temperature 14 and thinner GaAs p-i-n mesa photodiodes (2 lm) had $1keV FWHM at 60 C, 12 coupled to similar front-end electronics. The improving of the energy resolution was attributed to slightly lower electronic noise arising from the preamplifier in adittion to better electrical characteristics (leakage current and capacitance) of the detector compared to those previously reported.…”

“…High temperature (up to 90 C) X-ray detection characterization of GaAs p þ -i-n þ diodes (2 lm thick i-layer) has been reported. 12 Furthermore, the X-ray detection of GaAs p þ -i-n þ diodes (3 lm thick i-layer) as a function of photon energy at 33.3 C was studied. 13 A fabrication study of GaAs mesa photodiodes regarding the effects of the wet chemical etchants and etch depths on the dark currents has also been reported.…”