Research activity

Testing of materials

Spectral performance and radiation hardness of a Si pin photodiode

Contact: Alíz Simon, a.simon (at)

Advanced materials are being evaluated for use as novel radiation detectors and microelectronic devices. Use of a nuclear microprobe has allowed spatially resolved electrical properties of the detector material to be measured. Nuclear microprobe analysis is playing an increasingly prominent role in the analysis of detector materials and devices by ion beam induced charge (IBIC) collection technique [70].

We have been investigating systematically the influence of radiation damage on the detection properties of a Si PIN diode with high lateral resolution from the point of view of microbeam applications [71]. It is known that irradiation creates new energy levels in the forbidden energy gap of the detector material, which brings about changes in the leakage current, the capacitance, and charge collection efficiency (CCE). Recently an empirical model has been developed [72] to describe the radiation damage. Equations are derived for the variations of the normalized peak position and peak width. The derived empirical equations are physically correct, as far as they account for the superposition of the influence of charge carrier trapping by native and radiation-induced defects and for the effect of charge carrier velocity saturation with electric field strength, as well.

IBIC map at 0V bias. The full irradiated area (340 x 340 µm2) is shown including the individually irradiated 100 x 100 µm2 squares by fluences from bottom to top and right to left: 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2 and 5 x 1011 ion/cm2, respectively.

Pulse height amplitude spectra obtained from 40 x 40 µm2 central squares at various fluences of 2005 keV protons, U=0 V.


[70] M.B.H. Breese, D.N. Jamieson, P.J.C. King: Materials Analysis using a Nuclear Microprobe, Wiley and Sons, New York, 1996.

[71] A. Simon, G. Kalinka, M. Jakšić, Ž. Pastuović, M. Novák, Á.Z. Kiss: Investigation of radiation damage in a Si PIN photodiode for particle detection, Nucl. Instr. and Meth. B 260 (2007) 304

[72] G. Kalinka, M. Novák, A. Simon, Ž. Pastuović, M. Jakšić, Á.Z. Kiss: Empirical approach to the description of spectral performance degradation of silicon photodiodes used as particle detectors, Nucl. Instr. and Meth. B 267 (2009) 2203