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

© 2016 Author(s). Results characterising the performance of thin (2 μm i-layer) Al0.52In0.48P p+-i-n+ mesa photodiodes for X-ray photon counting spectroscopy are reported at room temperature. Two 200 μm diameter and two 400 μm 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/cm2 were observed at 30 V (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 μs shaping time, with the device illuminated by an 55Fe radioisotope X-ray source. Experimental results showed that the best energy resolution (FWHM) achieved at 5.9 keV was 930 eV for the 200 μm Al0.52In0.48P diameter devices, when reverse biased at 15 V. System noise analysis was also carried out, and the different noise contributions were computed.