Characterisation of Al0.52In0.48P mesa p-i-n photodiodes for X-ray photon counting spectroscopy

Results characterising the performance of thin (2 lm i-layer) Al0.52In0.48P p(+)-i-n(+) mesa photodiodes for X-ray photon counting spectroscopy are reported at room temperature. Two 200 lm diameter and two 400 mu m diameter Al0.52In0.48P p(+)-i-n(+) mesa photodiodes were studied. Dark current results as a function of applied reverse bias are shown; dark current densities <3 nA/cm(2) were observed at 30V (150 kV/cm) for all the devices analysed. Capacitance measurements as a function of applied reverse bias are also reported. X-ray spectra were collected using 10 mu s shaping time, with the device illuminated by an Fe-55 radioisotope X-ray source. Experimental results showed that the best energy resolution (FWHM) achieved at 5.9 keV was 930 eV for the 200 mu m Al0.52In0.48P diameter devices, when reverse biased at 15V. System noise analysis was also carried out, and the different noise contributions were computed. Published by AIP Publishing.