High-Power SiC Diodes: Characteristics, Reliability and Relation to Material Defects

The carbon vacancy (V C ) has been suggested by different studies to be involved in the Z 1 /Z 2 defect-a carrier lifetime killer in SiC. However, the correlation between the Z 1 /Z 2 deep level with V C is not possible since only the negative carbon vacancy (V − C ) at the hexagonal site, V − C (h), with unclear negative-U behaviors was identified by electron paramagnetic resonance (EPR). Using freestanding n-type 4H -SiC epilayers irradiated with low energy (250 keV) electrons at room temperature to introduce mainly V C and defects in the C sublattice, we observed the strong EPR signals of V − C (h) and another S = 1/2 center. Electron paramagnetic resonance experiments show a negative-U behavior of the two centers and their similar symmetry lowering from C 3v to C 1h at low temperatures. Comparing the 29 Si and 13 C ligand hyperfine constants observed by EPR and first principles calculations, the new center is identified as V − C (k). The negative-U behavior is further confirmed by large scale density functional theory supercell calculations using different charge correction schemes. The results support the identification of the lifetime limiting Z 1 /Z 2 defect to be related to acceptor states of the carbon vacancy.

show abstract

“…In the stable configuration [Figs. 9(a) and 9(c)], the spin density is localized on two Si atoms in the basal plane [Si 3,4 in Fig. 9(a)].…”

Section: Centermentioning

confidence: 99%

“…3 In such high-voltage power devices, a long carrier lifetime is required for effective modulation of the conductivity of very thick blocking-voltage layers. For example, a lifetime longer than 5 μs will be required for effective conductivity modulation in 10 kV SiC PiN diodes.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

show abstract

“…The presence of a high excess carrier concentration which contributes to conductivity is governed by carrier lifetime. Long carrier lifetime under high injection condition is required to obtain effective conductivity modulation that helps to reduce the on-state resistance [66][67][68]. For high-voltage device, a higher operating voltage requires a thicker layer to block the voltage and longer carrier lifetime is needed.…”

Section: Carrier Lifetime In Sicmentioning

confidence: 99%

Electron Paramagnetic Resonance Studies of Point Defects in AlGaN and SiC

Trinh¹

2015

Linköping Studies in Science and Technology. Dissertations

View full text Add to dashboard Cite

Point defects in semiconductor materials are known to have important influence on the performance of electronic devices. For defect control, knowledge on the model of defects and their properties is required. Information on defects, such as the symmetry and the localization of spins, is essential for identification of defects and understanding their electronic structure. Such information can be obtained from Electron Paramagnetic Resonance (EPR). In many cases, the energy levels of defects can be determined from photoexcitation EPR (photo-EPR) or temperature dependence of the EPR signal. The thesis contains six papers, focusing on the identification and electronic structure investigation of defects and impurities in Al x Ga 1-x N (x~0.7-1) and silicon carbide (SiC) using EPR in combination with other electrical characterizations and density functional theory calculations.The two first papers concern EPR studies of silicon (Si) in AlGaN alloys. Due to its direct and wide band gap which can be tailored from 3.4 eV for GaN to 6.2 eV for AlN, high-Al-content wurtzite Al x Ga 1-x N (x≥0.7) has been considered as a promising material for fabrication of compact, highefficiency and non-toxic deep ultraviolet light-emitting diodes (LEDs) and laser diodes (LDs) for replacing low-efficiency and toxic mercury lamps in water/air purification and sterilization. Si is commonly used for n-type doping in AlGaN and AlN, but the conductivity of Si-doped Al x Ga 1-x N was often reported to drop abruptly at high Al content (x>0.7) and the reason was often speculated to be due to either carrier compensation by other deep levels or Si itself when it transforms from a shallow donor to a DX (or negative-U) center which acts as an acceptor. In paper 1, we showed that Si already forms a stable DX center in Al x Ga 1-x N with x ~0.77. However, with the Fermi level locating only ~3 meV below the neutral charge state, E d , Si still behaves as a shallow donor. Negligible carrier compensation by oxygen (O) in Al 0.77 Ga 0.23 N:Si layers was observed, suggesting that at such Al content, O does not seem to hinder the n-type doping in the material. In paper 2, we found the coexistence of two Si DX centers, the stable DX1 and the metastable DX2, in Al x Ga 1-x N for x≥0.84. For the stable DX1 center, abrupt deepening of the energy level of the negative charge state DX -, E DX , which determines the ionization energy E a of the Si donor, with increasing of the Al content for x≥0.83 was observed. The dependence of E a on the Al content in Al x Ga 1-x N:Si layers (0.79≤x≤1) was determined. The results explain the drastic decrease of the conductivity as often reported for Al x Ga 1-x N:Si in previous transport studies. For the metastable DX2 center, we found that the E DX level remains close to E d for x=0.84÷1.SiC is a wide band-gap semiconductor having high-thermal conductivity, high breakdown field, and large saturated electron drift velocity which are iv essential properties for high-voltage and high-power devices. In paper 3, the identif...

show abstract

“…Benefits on the on-state resistance are expected for bipolar devices owning to the effect of conductivity modulation. 3,4 Despite the enthusiasm of developing very high voltage devices, the industrial development of SiC bipolar is facing some problems. One of these is the degradation of bipolar devices during operation.…”

Section: Introductionmentioning

confidence: 99%

Application of UV photoluminescence imaging spectroscopy for stacking faults identification on thick, lightly n-type doped, 4°-off 4H-SiC epilayers

et al. 2015

View full text Add to dashboard Cite

This paper deals with the description and the application of an original photoluminescence (PL) imaging technique on thick, lighly n-type doped 4H-SiC epilayers for in-grown stacking fault (SF) identification. This technique, call “photoluminescence imaging spectroscopy” (PLIS), compares different PL imaging pictures in order to create a new picture which displays the location and an approximation of the maximum photoemission wavelength of SFs at room temperature. Five types of SF have been detected and identified by PLIS on two different wafers. The origin of SF type modification during the growth is also discussed in this work.

show abstract

High-Power SiC Diodes: Characteristics, Reliability and Relation to Material Defects

Cited by 157 publications

References 0 publications

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

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

Electron Paramagnetic Resonance Studies of Point Defects in AlGaN and SiC

Application of UV photoluminescence imaging spectroscopy for stacking faults identification on thick, lightly n-type doped, 4°-off 4H-SiC epilayers

Contact Info

Product

Resources

About