Nitrogen Ion Implantation and Thermal Annealing in 6H–SiC Single Crystal

Abstract

The interrelationships among implantation-induced defect density, carrier activation rate, substrate temperature during nitrogen implantation and annealing in 6H–SiC have been clarified. Several defects, whose energy required for recovery of lattice damage depends on the substrate temperature during implantation, were examined. Although defect density was sufficiently low that it was undetectable by Rutherford backscattering spectrometry, the carrier activation rate was 3.3% under the condition that the implanted nitrogen density was 1.8×1019 cm-3. According to the first principles local-density functional calculation using the cubic SiC crystal model, the complex defect composed of interstitial carbon and substituted nitrogen, which produces a localized electronic state and a half-occupied level in the band gap, is considered to be one cause of the low carrier activation rate in nitrogen-implanted SiC.

First-principles study of n-type dopants and their clustering in SiC

“…That the N͑C͒ configuration is energetically more favorable is in agreement with experimental observations, but the difference of formation energies for N͑Si͒ and N͑C͒ configurations is larger than that obtained in the previous theoretical study of Miyajima et al 6 The origin for this discrepancy may be attributed to the different approximations used in Ref. 6, although a rigorous analysis is not possible since details of their calculations were not given. As expected, the most stable charge state of the dopant at zero temperature depends on the position of the electron chemical potential e .…”

“…However, a N atom at a Si lattice site relaxes to an off-center position, which is ϳ0.4 Å from the perfect lattice Si site, lengthening the bond to one of the nearest neighbors and shortening the remaining three bonds, in agreement with previous results. 6,7 We predict that a N substitutional is most stable by far at a N͑C͒ site; the energy difference between the N͑Si͒ and N͑C͒ is approximately 6 eV throughout the range of doping conditions. That the N͑C͒ configuration is energetically more favorable is in agreement with experimental observations, but the difference of formation energies for N͑Si͒ and N͑C͒ configurations is larger than that obtained in the previous theoretical study of Miyajima et al 6 The origin for this discrepancy may be attributed to the different approximations used in Ref.…”

“…6,7 We predict that a N substitutional is most stable by far at a N͑C͒ site; the energy difference between the N͑Si͒ and N͑C͒ is approximately 6 eV throughout the range of doping conditions. That the N͑C͒ configuration is energetically more favorable is in agreement with experimental observations, but the difference of formation energies for N͑Si͒ and N͑C͒ configurations is larger than that obtained in the previous theoretical study of Miyajima et al 6 The origin for this discrepancy may be attributed to the different approximations used in Ref. 6, although a rigorous analysis is not possible since details of their calculations were not given.…”

Electronic structure of the nitrogen donors in 6H SiC as studied by pulsed ENDOR and TRIPLE ENDOR spectroscopy

“…The first principle local‐density functional calculations 33 for the N atom on C and Si sites indicates that due to the different charge density distributions around the N atom on C and Si site the N C center acts as a shallow donor while the N Si center due to the strong localization of the wave function does not constitute a shallow donor state. This conclusion is consistent with the distribution of the electronic wave function around N donor found for N k1 and N k2 from ENDOR measurements.…”

Influences of postimplantation annealing conditions on resistance lowering in high-phosphorus-implanted 4H–SiC

“…[5][6][7][8] However, implanted N atoms tend to be electrically inactive at a N concentration of more than 2 ϫ10 19 cm Ϫ3 due to the molecules and/or precipitates they form during postimplantation annealing. [5][6][7][8] However, implanted N atoms tend to be electrically inactive at a N concentration of more than 2 ϫ10 19 cm Ϫ3 due to the molecules and/or precipitates they form during postimplantation annealing.…”