Detection of pulsed ionizing radiation with the aid of variable-gap structures

An investigation is reported of the feasibility of using variable-gap structures as luminescence-based detectors of pulsed x-ray and gamma radiation in small volumes of semiconductor devices. It is shown that the effective thickness of the sensitive region deff depends on a number of parameters of a sample such as the band gap gradient, the thicknesses of the substrate and the variable-gap layer, the energy of the luminescence maximum on the narrow-gap side of the layer, and the band gap of the substrate. Removal of some of the substrate or of the layer from the narrow-gap side can be used to vary deff from few microns to tens of microns. Experimental results reported for silicon-doped AlxGa1-xAs/GaAs structures subjected to pulsed irradiation confirm that they can be used to detect short (∼10-8 s) gamma-ray pulses