Doping of n-type 6H–SiC and 4H–SiC with defects created with a proton beam

Abstract

Deep centers in n-type 4H–SiC and 6H–SiC irradiated with 8 MeV protons have been investigated by capacitance spectroscopy and electron paramagnetic resonance (EPR). Samples were fabricated by sublimation epitaxy or commercially produced by CREE Inc. Research Triangle Park, NC. It is showed that irradiation of wide-band gap semiconductors may lead to an increase in the concentration of uncompensated donors in an n-type material. The spectrum of deep centers in both SiC polytypes is independent of the technology of material growth or type of charged particles. However, the parameters and behavior of the radiation defects in 6H– and 4H–SiC are different. A conclusion about the possible nature of the irradiation induced centers is made on the basis of annealing behavior and EPR data. The obtained results show that proton irradiation can be used in SiC device fabrication technology for producing local high-resistance regions in the semiconductor.

Vacancy Defects Detected by Positron Annihilation

“…An annealing study of neutron irradiated 4H-SiC using ESR and optical absorption showed that the optical transition at 780 nm (1.59 eV), which is comparable to the RD 4 energy level, is originating from V Si [83]. The RD 5 levels at around E C -0.5 eV in 6H-SiC (same as L 6 , E i ) [54,57,58,63,66] are reported to show the similar annealing behavior to V C below 500…”

“…As for the other energy levels, the R levels appearing at E C -1.1∼1.3 eV in 6H-SiC (same as E 7 and L 10 ) [54,57,63] are attributed to V Si in the PAS study [44]. The R level shown in Fig.…”

“…Since the thermal stability of V C induced by irradiation is well below than those of the E 1/2 in 6H-SiC, it seems to be a bit difficult to attribute these levels to V C . The Z 1/2 in 6H-SiC and RD 1/2 in 4H-SiC were proposed to be related to either V Si [56,82] or divacancies V Si VC [63]. However, the Z 1/2 in 6H-SiC and RD 1/2 in 4H-SiC are fully annealed above 1000…”

“…In the previous studies, V C was thought to be the candidate for the E 1/2 in 6H-SiC [56,63]. In the CVD process studies, the Z 1/2 in 4H-SiC was correlated with the excess Si (e.g., V C and SiC) [78]- [80] or the excess C (e.g., I C ) and nitrogen doping [81].…”

Irradiation and annealing of p-type silicon carbide

“…By comparing the removal rates of holes in various SiC polytypes (see table 1), we find that the acceptor compensation is more efficient for the 6H polytype than for the 4H polytype. We have shown previously that these ratios are inverted for the n-type material and the removal rate of electrons for the 4H polytype is several times that for the 6H polytype [15].…”