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The relatively low value of the number of electron-hole (e-h) pairs per micron for Minimum Ionizing Particles (MIPs) in SiC against the value for Si, imposes severe constrains on the crystallographic quality, the thickness and the doping concentration of the SiC epitaxial layer used as detection medium. In this work, a 85 μm thick 4H-SiC epitaxial layer with a low doping concentration, Neff ≤ 1 × 1014 cm-3, was used in order to have a high number (≈4700) of e-h pairs generated by a MIP in the active region. We present experimental data on the charge spectrum for β MIPs from a 90Sr source, collected in a temperature range from room temperature up to 81°C. [ABSTRACT FROM AUTHOR]

We report the results of an experimental study on the radiation hardness of 4H-SiC diodes used as α-particle detectors with 1 MeV neutrons up to a fluence of 8 × 1015 n/cm². As the irradiation level approaches the range 1015 n/cm², the material behaves as intrinsic due to a very high compensation effect and the diodes are still able to detect with a reasonable good Charge Collection Efficiency (CCE = 80%). For fluences > 1015 n/cm² CCE decreases monotonically to ≈ 20 % at the highest fluence. Heavily irradiated SiC diodes have been studied by means of Photo Induced Current Transient Spectroscopy (PICTS) technique in order to characterize the electronic levels associated with the irradiation-induced defects. The dominant features of the PICTS spectra occur between 400–700 K; in this temperature range the deep levels associated with the induced defects play the main role in degradation of the CCE. Enthalpy, capture cross-section and concentration of such deep levels were calculated and we found that two deep levels (Et = 1.18 eV and Et = 1.50 eV) are responsible for the decrease in CCE. They have been associated to an elementary defect involving a carbon vacancy and to a defect complex involving a carbon and a silicon vacancy, respectively. [ABSTRACT FROM AUTHOR]

Particles detectors were made using semiconductor epitaxial 4H-SiC as the detection medium. The investigated detectors are formed by Schottky contact (Au) on the epitaxial layer and an ohmic contact on the backside of 4H-SiC substrates with different micropipe densities from CREE. For radiation hardness studies, the detectors have been irradiated with electrons (8.2 MeV) and γ-rays (60Co source) at fluences and doses ranging from 0 to 9.48×1014 e/cm2 and 40 Mrad, respectively. We present experimental data on the charge collection properties by using 4.14 MeV α-particles impinging on the Schottky contact. Hundred percent Charge Collection Efficiency, CCE, is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the α-particle projected range, even after the irradiation at the highest dose. By comparing measured CCE values with the outcomes of drift–diffusion simulations, values are inferred for the hole lifetime, τp, within the neutral region of the charge carrier generation layer. τp was found to decrease with increasing radiation levels, ranging from 300 ns in non-irradiated detectors to 3 ns in the most irradiated ones. The diffusion contribution of the minority charge carriers to CCE is pointed out. [Copyright &y& Elsevier]

The development of SiC minimum ionising particle (MIP) detectors imposes severe constrains in the electronic quality and the thickness of the material due to the relatively high value of the energy required to produce an electron–hole pair in this material by MIP against the value for Si. In this work, particle detectors were made using semiconductor epitaxial undoped n-type 4H-SiC as the detection medium. The thickness of the epilayer is on the order of 40 μm and the detectors are realised by the formation of a nickel silicide on the silicon surface of the epitaxial layer (Schottky contact) and of the ohmic contact on the back side of 4H-SiC substrate. The low doping concentration (≅6×1013 cm−3) of the epilayer allows the detector to be totally depleted at relatively low reverse voltages (≅100 V). We present experimental data on the charge collection properties by using 5.486 MeV α-particles impinging on the Schottky contact. A 100% charge collection efficiency (CCE) is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the α-particle extrapolated range in SiC. The diffusion contribution of the minority change carriers to CCE is pointed out. By comparing measured CCE values to the outcomes of drift–diffusion simulation, values are inferred for the hole lifetime within the neutral region of the charge carrier generation layer. [Copyright &y& Elsevier]

Particle detectors were made using semiconductor epitaxial 4H–SiC as the detection medium. The investigated detectors are formed by Schottky contact (Au) on the epitaxial layer and an ohmic contact on the back side of 4H–SiC substrates with different micropipe densities from CREE. For radiation hardness studies, the detectors have been irradiated with protons (24 GeV/c) at a fluence of about 1014 cm−2 and with electrons (8.2 MeV) and gamma-rays (60Co source) at doses ranging from 0 to 40 Mrad. We present experimental data on the charge collection properties by using 5.48, 4.14 and 2.00 MeV α-particles impinging on the Schottky contact. Hundred percent charge collection efficiency (CCE) is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the α-particle projected range, even after the irradiation at the highest dose. By comparing measured CCE values with the outcomes of drift–diffusion simulations, values are inferred for the hole lifetime, τp, within the neutral region of the charge carrier generation layer. τp was found to decrease with increasing radiation levels, ranging from 300 ns in non-irradiated detectors to 3 ns in the most irradiated ones. The diffusion contribution of the minority charge carriers to CCE is pointed out. [Copyright &y& Elsevier]

Presents a silicon carbide (SiC) sensor with high energy resolution in X-ray spectroscopy over a wide temperature range. Sensor composed of a Schottky barrier diode on high resistivity epitaxial SiC; Extremely low noise due to its ultra-low reverse current density even at high operating temperature; Equivalent noise charges as low as 17 electrons rms at 27 degrees C and 47 electrons rms at 100 degrees C.

Epitaxial SiC devices have been tested as radiation detectors for minimum ionising particles. The devices used are based on a commercial 4H–SiC epitaxial n-type layer deposited onto a 4H–SiC n+ type substrate wafer doped with nitrogen. Single-pad Schottky contacts have been produced by deposition of a 1000-A˚ gold film on the epitaxial layer using a lift-off technology and ohmic contacts have been deposited on the rear substrate side. The capacitance–voltage characteristics have been measured to determine the net effective doping in the space charge layer and the maximum active thickness of the devices. The measurements showed possible non-uniformity in the net doping of the epitaxial layer. The charge collection efficiency (CCE) has been tested by means of a 0.1 mCi 90Sr β-source. A 100% CCE is measured at the maximum active thickness, which is achieved above approximately 400 V. The charge signal of the SiC devices is stable and reproducible, with no evidence of priming or polarisation effects, due to the high crystalline quality of the epitaxial layer. [Copyright &y& Elsevier]

Several new technological applications of silicon carbide have attracted significant attention in recent years. As a wide gap semiconductor it has the capability to be used as a room temperature radiation detector. For most applications, material properties like homogeneity of charge transport, presence of defects, resistance to radiation damage, influence of light impurities (such as hydrogen) are of prime importance. Two different kinds of samples, crystalline (4H–SiC) and thin, amorphous (a-Si1−xCx:H) films, were studied using ion beam techniques. In the case of SiC single crystal radiation detectors, Li and proton beams with a wide range of energies were used to probe the charge collection efficiency at different device depths using the ion beam induced charge technique. Thin, amorphous and microcrystalline Si1−xCx:H films with a different stoichiometry and different degrees of structural ordering were examined using RBS and ERDA. [Copyright &y& Elsevier]

Native or process-induced defective states may significantly affect the transport properties of silicon carbide devices. For this reason, it is of major importance to detect them and, when possible, to identify their origin. This contribution deals with the deep levels detected by deep level transient spectroscopy analyses in silicon carbide Schottky detectors. Current–voltage and capacitance–voltage characteristics have also been studied to investigate Schottky barrier properties and diode quality. On the basis of the comparison with literature data, some of the deep levels found can be attributed to impurities introduced during growth. [Copyright &y& Elsevier]