Deep level transient spectroscopic and Hall effect investigation of the position of the vanadium acceptor level in 4H and 6H SiC

Abstract

Hall effect, deep level transient spectroscopy (DLTS) and optical absorption measurements were employed in concert to determine the position of the vanadium acceptor level in vanadium and nitrogen doped 6H and 4H SiC. Hall effect results indicate that the acceptor position in 4H SiC is at 0.80 eV beneath the conduction band edge, and 0.66 eV for the 6H polytype. The DLTS signature of the defect in the 4H polytype showed an ionization energy of 0.80 eV and a capture cross section of 1.8×10−16 cm−2. The optical absorption measurements proved that the levels investigated are related to isolated vanadium, and therefore the vanadium acceptor level. Based on the DLTS measurements and secondary ion mass spectroscopy data, the maximum solubility of vanadium in SiC was determined to be 3.0×1017 cm−3. At these incorporation limits and with the depth of the level, the vanadium acceptor level could be used in the creation of semi-insulating silicon carbide.

Electrically active point defects in n-type 4H–SiC

“…Initially, Cr and V were considered strong candidates for the origin of these levels as they have been reported at 0.74 and 0.80 eV below E c , respectively, and also have displayed high thermal stability as the incorporation of the impurity takes place either during the sublimation growth 3 or through ion implantation and postannealing at temperatures above 1300°C. 7 SIMS analysis coupled with the electrical depth profiling reveals that there is insufficient Cr in our samples to account for this level, which reaches concentrations у2 ϫ10 14 cm Ϫ3 after annealing of samples irradiated with electron doses у1ϫ10 15 cm Ϫ2 .…”

“…Identification of these low concentration impurities and their associated positions in the electronic band gap can be complicated by the high doping concentrations (у10 18 cm Ϫ3 ) typically found in bulk samples which make the formation of either a p-n or Schottky-type diode difficult. Recently, Jenny et al 3,4 have reported the position of the vanadium acceptor level at E c Ϫ0.80 eV through the incorporation of the metallic impurity during sublimation growth while Achtziger et al have reported on the Cr level at E c Ϫ0.74 eV through the use of ion-implanted radioactive isotopes. 7 The identification and characterization of intrinsic defects, however, have received less attention.…”

New materials for radiation hard semiconductor dectectors

“…When acting as a deep acceptor, vanadium forms a level at an energy 0.8 -1.0 eV below the conduction band, with the exact energy depending on the polytype (Jenny et al 1996), and compensates the shallow donors introduced by impurities from the growth process (Schneider et al 1990). The dominant vanadium donor state has been attributed to a level at 1.6 -1.7 eV below the conduction band (Mitchel et al 1999).…”

A Study of Deep Defect Levels in Semi-Insulating SiC Using Optical Admittance Spectroscopy

“…[3][4][5][6][7][8] Photo-ESR spectroscopy indicated that the vanadium donor level is located at E v + 1.6 eV in 6H-SiC. 3 Evwaraye and co-workers conducted OAS measurements below room temperature and reported vanadium donor levels at E v + 1.73 eV and E v + 1.55 eV in n-type 4H-SiC and p-type 6H-SiC, respectively.…”

“…7 Jenny and co-workers attribute the activation energy of 0.66 eV deduced from the temperature-dependent Hall resistivity to the V 3+/4+ level in 6H-SiC and reported the acceptor position to be 0.80 eV below the conduction band edge in 4H-SiC. 8 As stated earlier, calculations predict that vanadium complexes will also produce levels within the bandgap of 4H SiC. Evwaraye and co-workers reported that peaks at 1.17 eV in 4H-SIC and 1.13 eV in 6H-SiC are most likely a vanadium complex.…”