Performance of neutron-irradiated 4H-silicon carbide diodes subjected to alpha radiation

Abstract

The unique electrical and material properties of 4H-silicon-carbide (4H-SiC) make it a promising candidate material for high rate particle detectors. In contrast to the ubiquitously used silicon (Si), 4H-SiC offers a higher carrier saturation velocity and larger breakdown voltage, enabling a high intrinsic time resolution and mitigating pile-up effects. Additionally, as radiation hardness requirements grow more demanding in the context of future high luminosity high energy physics experiments, wide-bandgap materials such as 4H-SiC could offer better performance due to low dark currents and higher atomic displacement thresholds. In this work, the detector performance of 50 µm thick 4H-SiC p-in-n planar pad sensors was investigated at room temperature, using an 241Am alpha source at reverse biases of up to 1100 V. Samples subjected to neutron irradiation with fluences of up to 1 × 1016 neq/cm2 were included in the study in order to quantify the radiation hardness properties of 4H-SiC. A calibration of the absolute number of collected charges was performed using a GATE simulation. The obtained results are compared to previously performed UV transient current technique (TCT) studies. Samples exhibit a drop in charge collection efficiency (CCE) with increasing irradiation fluence, partially compensated at high reverse bias voltages far above full depletion voltage. At fluences of 5 × 1014 neq/cm2 and 1 × 1015 neq/cm2, CCEs of 64 % and 51 % are obtained, decreasing to 15 % at 5 × 1015 neq/cm2. A plateau of the collected charges is observed in accordance with the depletion of the volume the alpha particles penetrate for an unirradiated reference detector. For the neutron-irradiated samples, such a plateau only becomes apparent at higher reverse bias, roughly 600 V and 900 V for neutron fluences of 5 × 1014 neq/cm2 and 1 × 1015 neq/cm2. For the highest investigated fluence, CCE behaves almost linearly with increasing reverse bias. Compared to UV-TCT measurements, the reverse bias required to deplete a sensitive volume covering full energy deposition is lower, due to the small penetration depth of the alpha particles. At the highest reverse bias, the measured CCE values agree well with earlier UV-TCT studies, with discrepancies between 1% and 5%.

Neutron radiation induced effects in 4H-SiC PiN diodes

“…In reverse bias, charge collection efficiencies above 80 % can be obtained for fluences up to 1 × 10 15 n eq /cm 2 . This is slightly higher than previously published results for the same samples [8] and can be attributed to the usage of a charge-sensitive amplifier (CSA) instead of…”

“…In this work, the effect of neutron radiation damage on 4H-SiC p-n diodes is evaluated in an electrical characterization (section 3.1) as well as in charge collection efficiency measurements (section 3.2) The work builds on recent investigations using UV-TCT [7] and alpha particles [8] using the same devices. However, new measurements of particle detection in forward bias and data obtained with a 62.4 MeV proton beam are presented.…”

Position-resolved charge collection of silicon carbide detectors with an epitaxially-grown graphene layer

“…To study the prototypes described in the previous section, the transient current and charge collection are studied by irradiating the devices under a radioactive source 14 , 15 , and by means of the transient current technique (TCT) 16 , 17 .…”

Pulsed RF knock-out extraction: a potential enabler for FLASH hadrontherapy in the Bragg peak

“…The detectors were fabricated on a 4H-SiC substrate with a 50 µm thick epitaxially grown, n-doped active layer and had an active area of 3 × 3 mm 2 . More details on the employed detectors are given in Christanell et al (2022), Gaggl et al (2022aGaggl et al ( , 2023. The detector was positioned in the iso-center in air in the plateau region in the Bragg curve.…”