Development of AlGaAs avalanche diodes for soft X-ray photon counting

We report on the performance of avalanche photodiodes (APDs) based on the wide band gap material AlGaAs which have been developed for soft X-ray spectroscopy applications. A number of diode types with different layer thicknesses have been characterised. The temperature dependence of the avalanche multiplication process at soft X-ray energies in Al 0.8Ga 0.2As APDs was investigated at temperatures from +80°C to -20°C. X-ray spectra from a 55Fe radioactive source show these diodes can be used for spectroscopy with promising energy resolution (0.9-2.5keV) over a wide temperature range. The temperature dependence of the pure electron initiated multiplication factor (M e) and the mixed carrier initiated avalanche multiplication factor (M mix) were experimentally measured. The experimental results are compared with a spectroscopic Monte Carlo model for Al 0.8Ga 0.2As diodes from which the temperature dependence of the pure hole initiated multiplication factor (M h) is determined. © 2011 IEEE.