Defect levels and types of point defects in high-purity and vanadium-doped semi-insulating 4H–SiC

Abstract

Electron paramagnetic resonance (EPR) spectroscopy and photo-induced EPR are used to examine the point defects in vanadium-doped 4H-SiC and high-purity semi-insulating (HPSI) 4H-SiC grown by physical vapor transport. Both types of samples often exhibit a 1.1-eV activation energy, E a , as extracted from the temperature-dependent Hall/resistivity measurements; however, different defects are related to the same E a in each case. In the vanadium-doped wafers, the EPR data reveal both V 4+ and V 3+ in the same sample; thus, the 1.1-eV Hall activation energy is tentatively interpreted as the V 3+/4+ acceptor level. However, this conclusion cannot be confirmed because additional defects complicate the photoresponse of vanadium. The carbon vacancy, which is detected in all the HPSI wafers, exhibits a range of photothresholds similar to the various values measured for E a . The photo-EPR and temperature-dependent Hall/resistivity measurements made before and after a 1600°C anneal suggest that several different types of nonuniformly distributed defects participate in compensation of the HPSI material and that annealing selectively removes those with different defect levels.

Electrical properties of unintentionally doped semi-insulating and conducting 6H-SiC

“…Many different levels have been reported 3,4 and several intrinsic defects have been identified by electron paramagnetic resonance ͑EPR͒ studies [5][6][7] but correlations between electrical and EPR experiments have been difficult to make and remain controversial. Little has been published on the actual growth processes so it is also difficult to determine if the material is silicon or carbon rich during growth.…”

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

“…2 Also, the EPR spectrum of V 4+ in intentionally vanadium-doped SI 4H sample has been attributed to a complex. 19 Finally, we discuss the apparent contradiction between the measurement of E f (E c ) 1.1 eV in 4H and E c ) 0.8 eV in 6H) and the association of OAS peaks at 0.75 eV and 0.94 eV (4H) and 0.67 eV, 0.70 eV, and 0.87 eV (6H) with the removal of an electron from the vanadium acceptor level. Armed with the Hall data alone, we would be forced to conclude that these OAS peaks are not related to charge transfer from a defect to a band because the peaks occur at energies less than E f .…”

Growth of 2-Inch V-Doped Bulk 6H-SiC with High Semi-Insulating Yield

“…1,2 In general, the semi-insulating property of silicon carbide is realized by compensation of all shallow donors or acceptors with deep levels. In nominally undoped physical vapor transport (PVT)-grown SiC crystals, nitrogen is usually the main residual donor impurity, which is attributed to desorption of N 2 absorbed on porous graphite parts and SiC powder.…”