Ž. Pastuović

Temperature dependent TRIBIC in CZT detectors

Abstract Temperature dependence of the ion beam induced charge (IBIC) collection efficiency was studied in CdZnTe (CZT) in the range 166–330 K. A lateral surface between sputtered Au electrodes of the simple planar counter-grade CZT was irradiated by a focused 3 MeV proton microbeam. Measured charge collection efficiency profiles change with temperature. In order to understand better the charge collection mechanism at different temperatures time resolved ion beam induced charge (TRIBIC) technique was applied as well. Charge transients from the output of the preamplifier recorded by a fast storage oscilloscope showed that the electron transport is strongly influenced by temperature. Both IBIC and TRIBIC measurements showed negligible hole charge collection contribution in the studied detector.

Deep level defects in 4H-SiC introduced by ion implantation: the role of single ion regime

We characterized intrinsic deep level defects created in ion collision cascades which were produced by patterned implantation of single accelerated 2.0 MeV He and 600u2009keV H ions into n-type 4H-SiC epitaxial layers using a fast-scanning reduced-rate ion microbeam. The initial deep level transient spectroscopy measurement performed on as-grown material in the temperature range 150-700u2009K revealed the presence of only two electron traps, Z 1/2 (0.64u2009eV) and EH6/7 (1.84u2009eV) assigned to the two different charge state transitions of the isolated carbon vacancy, V C (=/0) and (0/+). C-V measurements of as-implanted samples revealed the increasing free carrier removal with larger ion fluence values, in particular at depth corresponding to a vicinity of the end of an ion range. The first DLTS measurement of as-implanted samples revealed formation of additional deep level defects labelled as ET1 (0.35u2009eV), ET2 (0.65u2009eV) and EH3 (1.06u2009eV) which were clearly distinguished from the presence of isolated carbon vacancies (Z 1/2 and EH6/7 defects) in increased concentrations after implantations either by He or H ions. Repeated C-V measurements showed that a partial net free-carrier recovery occurred in as-implanted samples upon the low-temperature annealing following the first DLTS measurement. The second DLTS measurement revealed the almost complete removal of ET2 defect and the partial removal of EH3 defect, while the concentrations of Z 1/2 and EH6/7 defects increased, due to the low temperature annealing up to 700u2009K accomplished during the first temperature scan. We concluded that the ET2 and EH3 defects: (i) act as majority carrier removal traps, (ii) exhibit a low thermal stability and (iii) can be related to the simple point-like defects introduced by light ion implantation, namely interstitials and/or complex of interstitials and vacancies in both carbon and silicon sub-lattices.

Ion beam induced charge analysis of radiation damage in silicon photodiodes

The ion beam induced charge (IBIC) technique is a valuable technique to study the degradation of the charge collection efficiency (CCE) induced by radiation damage in semiconductor devices. It offers the advantage of providing a wide range of damage levels generated by ions with different masses and energies in different regions of the same sample, and of using the same or different ions to probe the CCE degradation. This paper describes an experimental protocol based on IBIC and the relevant interpretative model, which includes the displacement damage dose approach as a special case and provides a general method to evaluate the effective radiation hardness of a material.

Double negatively charged carbon vacancy at the h- and k-sites in 4H-SiC: Combined Laplace-DLTS and DFT study

We present results from combined Laplace-Deep Level Transient Spectroscopy (Laplace-DLTS) and density functional theory studies of the carbon vacancy (VC) in n-type 4H-SiC. Using Laplace-DLTS, we were able to distinguish two previously unresolved sub-lattice-inequivalent emissions, causing the broad Z1/2 peak at 290u2009K that is commonly observed by conventional DLTS in n-type 4H-SiC. This peak has two components with activation energies for electron emission of 0.58u2009eV and 0.65u2009eV. We compared these results with the acceptor levels of VC obtained by means of hybrid density functional supercell calculations. The calculations support the assignment of the Z1/2 signal to a superposition of emission peaks from double negatively charged VC defects. Taking into account the measured and calculated energy levels, the calculated relative stability of VC in hexagonal (h) and cubic (k) lattice sites, as well as the observed relative amplitude of the Laplace-DLTS peaks, we assign Z1 and Z2 to VC(h) and VC(k), respectiv...