Radiation hardness of graded-gap AlxGa1−xAs X-ray detectors

A study is presented of the influence of alpha-particle irradiation on the current and optical responses of graded-gap AlxGa1−xAs detectors for alpha-particle and X-ray radiation. The current response of the detector decreases by about an order of magnitude at an irradiation dose of 1010 particles/cm2. Far better alpha-particle irradiation hardness is obtained from detectors with optical response. After an irradiation dose of 5×109 particles/cm2 the optical response has decreased by a factor of 1.5. Further increase of the radiation dose up to 4×1010 particles/cm2 produces almost no change in the detector sensitivity. The internal quantum efficiency of X-ray conversion to light remains nearly constant because the increase of non-radiative recombination is almost compensated by the increase of radiative recombination. A five-fold increase of the radiative recombination rate was observed at an irradiation dose of 1.8×1010 particles/cm2. The best alpha-particle irradiation hardness is obtained for detectors based on p-AlxGa1−xAs-n-GaAs structures with a p−n junction on the wide-gap side, when the thickness of the graded-gap AlxGa1−xAs layer is larger than the alpha-particle penetration depth.