4H-SiC Schottky barrier diodes as radiation detectors: a review

In this review paper, an overview of the application of n-type 4H-SiC Schottky barrier diodes (SBDs) as radiation detectors is given. We have chosen 4H-SiC SBDs among other semiconductor devices such as PiN diodes or metal-oxide-semiconductor (MOS) structures, as significant progress has been achieved in radiation detection applications of SBDs in the last decade. Here, we present the recent advances at all key stages in the application of 4H-SiC SBDs as radiation detectors, namely: SBDs fabrication, electrical characterization of SBDs, and their radiation response. The main achievements are highlighted, and the main challenges are discussed

Mogućnosti korištenja European Solar Radiation Atlasa na primjeru analize dnevnog kretanja Sunca

The application of the European Solar Radiation Atlas (ESRA) in daily Sun motion in sky analysis and its effects is widely spread in all engineering professions. Mathematical relations for Sun azimuth and height in specified moment, defined by date and time, can, for instance, be used in electrical engineering calculations of energy production and control of photovoltaic plants. The results obtained at measuring stations across Europe produce empirical relations between irradiation, time and electrical energy production. In this research a model of ostensible Sun movement trough daily analysis of its height and azimuth, and the analysis of production of integrated photovoltaic plant on the roof of the Technical College in Bjelovar with the web interface implementation of ESRA model for specified application – PVGIS (Photovoltaic Geographical Information Systems) are presented.Primjena European Solar Radiation Atlasa (ESRA) u analizama dnevnih kretanja Sunca po nebu i njegovih učinaka je rasprostranjena u svim inženjerskim strukama. Matematički odnosi visine i azimuta Sunca u određenom trenutku, defniranom datumom i vremenom, mogu se npr. u elektrotehnici koristiti za proračune proizvodnje i upravljanje fotonaponskim postrojenjem. Rezultati na mjernim stanicama širom Europe daju empirijske odnose zračenja, vremena i proizvodnje električne energije. U ovom radu je dan pregled modela za prividno kretanje Sunca kroz dnevnu analizu visine i azimuta Sunca, te analiza proizvodnje fotonaponskog postrojenja na krovu zgrade Visoke tehničke škole u Bjelovaru pomoću web sučelja implementacije ESRA modela za spomenutu primjenu – PVGIS (Photovoltaic Geographical Information Systems)

Non-linear behavior of Al-contacted pure amorphous boron (PureB) devices at low temperatures

Deposition of pure amorphous boron (PureB) layers on n-type Si results in p+n-like devices even in cases where B in-diffusion during the deposition is not expected. It is suspected that such behavior is due to the formation of an interfacial hole layer (IHL) between the PureB and Si. To further investigate physical mechanisms governing conduction of holes across the PureB/Si interface and through the IHL, electrical measurements were performed from room temperature down to cryogenic temperatures as low as 100 K. In this paper, current-voltage (I-V) measurements are made on structures where the PureB connects to p-type Si regions. One set of devices comprises ring-shaped structures designed for measuring the conductance through the IHL. In these structures, the PureB layer is deposited in rings that are contacted at the inner and outer perimeter with Al. Another set of samples includes devices where the PureB layer was deposited on p-type bulk Si. At room temperature, a close to linear change of current with voltage was seen irrespective of the PureB layer thickness and post-deposition processing. Lowering the operating temperature led to an increasingly non-linear I-V characteristics. Plausible explanations for the non-linear behavior are considered and discussed in the paper

Structural and Electrical Characterization of Pure and Al-Doped ZnO Nanorods

Pure and Al-doped (3 at.%) ZnO nanorods were prepared by two-step synthesis. In the first step, ZnO thin films were deposited on silicon wafers by spin coating ; then, ZnO nanorods (NR) and Al- doped ZnO NR were grown using a chemical bath method. The structural properties of zincite nanorods were determined by X-ray diffraction (XRD) and corroborated well with the morphologic properties obtained by field-emission gun scanning electron microscopy (FEG SEM) with energy- dispersive X-ray spectroscopy (EDS). Morphology results revealed a minute change in the nanorod geometry upon doping, which was also visible by Kelvin probe force microscopy (KPFM). KPFM also showed preliminary electrical properties. Detailed electrical characterization of pure and Al-doped ZnO NR was conducted by temperature-dependent current–voltage (I–V) measurements on Au/(Al)ZnO NR/n-Si junctions. It was shown that Al doping increases the conductivity of ZnO NR by an order of magnitude. The I–V characteristics of pure and Al-doped ZnO NR followed the ohmic regime for lower voltages, whereas, for the higher voltages, significant changes in electric conduction mechanisms were detected and ascribed to Al- doping. In conclusion, for future applications, one should consider the possible influence of the geometry change of (Al)ZnO NRs on their overall electric transport properties

Depth Profile Analysis of Deep Level Defects in 4H- SiC Introduced by Radiation

Deep level defects created by implantation of light-helium and medium heavy carbon ions in the single ion regime and neutron irradiation in n- type 4H-SiC are characterized by the DLTS technique. Two deep levels with energies 0.4 eV (EH1) and 0.7 eV (EH3) below the conduction band minimum are created in either ion implanted and neutron irradiated material beside carbon vacancies (Z1/2). In our study, we analyze components of EH1 and EH3 deep levels based on their concentration depth profiles, in addition to (−3/=) and (=/−) transition levels of silicon vacancy. A higher EH3 deep level concentration compared to the EH1 deep level concentration and a slight shift of the EH3 concentration depth profile to larger depths indicate that an additional deep level contributes to the DLTS signal of the EH3 deep level, most probably the defect complex involving interstitials. We report on the introduction of metastable M-center by light/medium heavy ion implantation and neutron irradiation, previously reported in cases of proton and electron irradiation. Contribution of M-center to the EH1 concentration profile is presented

Editorial for the special issue on “Crystalline materials for radiation detection: a new perspective”

The development of efficient and environmentally friendly technologies for radiationdetection is a great challenge. Among the materials of present and future perspective are crystalline materials, wide-bandgap semiconductor crystals

Acceptor levels of the carbon vacancy in 4H4H-SiC: combining Laplace deep level transient spectroscopy with density functional modeling

We provide direct evidence that the broad Z$_{1/2}$ peak, commonly observed by conventional DLTS in as-grown and at high concentrations in radiation damaged $4H$-SiC, has two components, namely Z$_{1}$ and Z$_{2}$, with activation energies for electron emission of 0.59 and 0.67~eV, respectively. We assign these components to $\mathrm{Z}_{1/2}^{=}\rightarrow\mathrm{Z}_{1/2}^{-}+e^{-}\rightarrow\mathrm{Z}_{1/2}^{0}+2e^{-}$ transition sequences from negative-$U$ ordered acceptor levels of carbon vacancy (V$_{\mathrm{C}}$) defects at hexagonal/pseudo-cubic sites, respectively. By employing short filling pulses at lower temperatures, we were able to characterize the first acceptor level of V$_{\mathrm{C}}$ on both sub-lattice sites. Activation energies for electron emission of 0.48 and 0.41~eV were determined for $\mathrm{Z}_{1}(-/0)$ and $\mathrm{Z}_{2}(-/0)$ transitions, respectively. Based on trap filling kinetics and capture barrier calculations, we investigated the two-step transitions from neutral to doubly negatively charged Z$_{1}$ and Z$_{2}$. Positions of the first and second acceptor levels of V$_{\mathrm{C}}$ at both lattice sites, as well as $(=\!/0)$ occupancy levels were derived from the analysis of the emission and capture data

M-center in low-energy electron irradiated 4H-SiC

We report on the low-energy electron irradiated 4H-SiC material studied by means of deep-level transient spectroscopy (DLTS) and Laplace-DLTS. Electron irradiation has introduced the following deep level defects: EH1 and EH3 previously assigned to carbon interstitial-related defects. We propose that EH1 and EH3 are identical to M1 and M3, also recently assigned to carbon interstitial defects, and assign them t