Physical aspects of precise spectrometry of α-particles with silicon pn-junction detectors

Abstract

Investigations of energy and charge losses have been carried out for silicon planar α-particle detectors. The detectors were manufactured by an advanced technology, using ion implantation and various annealing temperatures. A detailed analysis of the recombination processes in α-particle tracks with a high electron-hole density and a measurement procedure for the main parameters of charge carrier loss have been developed. The procedure consists in the measurement of the pulse amplitude deficit as a function of the reverse bias voltage and the tilting angle as well as in a special treatment for the determination of carrier lifetimes, surface recombination velocities and dead layers. The experimental data show a reduction of the dead layer to 200 Å, and of the energy resolution to 9–9.5 keV. The explanation implies possible changes of the doping profile due to acceptor diffusion under thermal treatment and the corresponding modification of the built-in field in the p +-layer. This effect suppresses the surface and Auger recombination of non-equilibrium carriers in tracks of α-particles.