Physical Aspects of Precise Spectrometry of alpha-particles with pn-Junction Detetors

Investigations of energy and charge losses have been carried out for silicon planar alpha-particle detectors. The detectors were manufactured by an advanced technology, using ion implantation and various anealing temperatures. A deteiled analysis of the recombination processes in alpha-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 leyer to 200 A, 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 alpha-particles.