Minimum ionizing and alpha particles detectors based on epitaxial semiconductor silicon carbide

The relatively high value of the energy required to produce an electron-hole pair in silicon carbide, SiC, by a minimum ionizing particle (MIP) against the value for Si, imposes severe constrains in the crystallographic quality, the thickness and the doping concentration of the SiC epitaxial layer used as the detection medium. In this work, a 40 μm thick 4 H-SiC epitaxial layer with a low doping concentration of ∼5×10¹³ cm^-3 was used in order to have a relatively high number (∼2200) of e-h pairs generated by a MIP and to deplete the total active layer at relatively low reverse bias (60 V). The detectors are realized by the formation of a nickel silicide (Ni₂Si) on the silicon surface of the epitaxial layer (Schottky contact) and of the ohmic contact on the backside of a 4 H-SiC heavily doped substrate. We present experimental data on the charge collection properties with α-particles from ²⁴¹Am and β-particles from ⁹⁰Sr. In both cases, a 100% charge collection efficiency, CCE, is demonstrated and the diffusion contribution of the minority charge carriers to CCE is pointed out. The charge spectrum for MIPs from ⁹⁰Sr shows a full detection efficiency with the pedestal (noise) clearly separated by the signal (Landau distribution) at reverse bias values comparable and higher than the one needed to totally deplete the layer. Moreover, no degradation was observed at 94°C in the CCE and in the energy resolution of the ²⁴¹Am alpha-signal from the SiC detector.