Minimum Ionizing and Alpha Particles Detectors Based on Epitaxial Semiconductor Silicon Carbide

Abstract

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 /spl mu/m thick 4 H-SiC epitaxial layer with a low doping concentration of /spl sim/5/spl times/10/sup 13/ cm/sup -3/ was used in order to have a relatively high number (/spl sim/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 (Ni/sub 2/Si) 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 /spl alpha/-particles from /sup 241/Am and /spl beta/-particles from /sup 90/Sr. 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 /sup 90/Sr 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/spl deg/C in the CCE and in the energy resolution of the /sup 241/Am alpha-signal from the SiC detector.