Sublimation-Grown Semi-Insulating SiC for High Frequency Devices

Abstract

In this paper we show the progression in the development of semi-insulating SiC grown by the sublimation technique from extrinsically doped material to high purity semi-insulating (HPSI) 4H-SiC bulk crystals of 2-inch and 3-inch diameter without resorting to the intentional introduction of elemental deep level dopants, such as vanadium. Secondary ion mass spectrometry, optical absorption, deep level transient spectroscopy and electron paramagnetic resonance data suggest that the semi-insulating behavior in HPSI material originates from deep levels associated with intrinsic point defects. While high temperature resistivity measurements on different high purity 4H-SiC samples indicate activation energies ranging from 0.9 to 1.6 eV, HPSI wafers with homogeneous activation energies near mid-gap are demonstrated. The room-temperature thermal conductivity of this material approaches the theoretical maximum of ~ 5 W/cmK. Additionally, HPSI substrates exhibit micropipe densities as low as 8 cm -2 over the full diameter of a 3-inch wafer. MESFETs produced on HPSI wafers are free of backgating effects and have resulted in the best combination of power density and efficiency reported to date for SiC MESFETs of 5.2 W/mm and 63% power added efficiency (PAE) at 3.5 GHz.

Negative-Ucarbon vacancy in 4H-SiC: Assessment of charge correction schemes and identification of the negative carbon vacancy at the quasicubic site

“…[27][28][29] The V + C center is a common defect in high-purity semi-insulating (HPSI) SiC substrates [30][31][32][33] and is suggested to be related to the EH 6/7 center. 29,34 The V C defect has been used for controlling the resistivity in commercial HPSI SiC substrates, 35,36 although the detailed mechanism of carrier compensation involving the C vacancy is still not clear. Among different intrinsic defects, V C and the divacancy have been suggested to be the most suitable defects for obtaining thermally stable semi-insulating properties in HPSI SiC substrates.…”

Vanadium doping using VCl4 source during the chloro-carbon epitaxial growth of 4H-SiC

“…Main approaches to achieving SI properties in SiC include (1) intentional vanadium (V) doping [3][4][5][6][7] and (2) use of deep levels caused by intrinsic defects [8][9][10][11][12][13]. Other transition metals such as iron (Fe) have also been investigated for producing resistive SiC substrates and epitaxial layers [14,15].…”

EPR andab initiocalculation study on the EI4 center in4H- and6H-SiC

“…In HPSI SiC substrates grown by hightemperature chemical vapor deposition ͑HTCVD͒ ͑Refs. 4-6͒ or by physical vapor deposition 7,8 semi-insulating ͑SI͒ properties have been achieved using intrinsic defects. In those materials, deep acceptor levels of vacancy-related defects can compensate the residual N shallow donors to pin the Fermi level to one of the deep levels and highly resistive materials with typical resistivity in the range of 10 6 -10 10 ⍀ cm can be achieved.…”

“…In those materials, deep acceptor levels of vacancy-related defects can compensate the residual N shallow donors to pin the Fermi level to one of the deep levels and highly resistive materials with typical resistivity in the range of 10 6 -10 10 ⍀ cm can be achieved. [4][5][6][7][8] There are different types of HPSI SiC materials characterized by different activation energies ranging from ϳ0.6 to ϳ1.6 eV. [4][5][6][7][8] It has been shown that carrier compensation processes in HPSI 4H-SiC materials are complicated, involving different defects of which the silicon vacancy ͑V Si ͒, the carbon vacancy ͑V C ͒, the carbon antisite-vacancy pairs ͑C Si V C ͒, and the divacancy ͑V C V Si ͒ are the most prominent ones.…”