Investigation of stress at SiO2/4H-SiC interface induced by thermal oxidation by confocal Raman microscopy

Stress at an SiO2/4H-SiC interface was investigated by using confocal Raman microscopy. Measurements were gathered while sequentially etching the SiO2 film on 4H-SiC. A shift of the folded transverse optical E2 mode peak toward low wavenumbers was observed in a 50 nm thick SiO2/4H-SiC, and this shift remained constant for samples with an SiO2 thickness greater than 10 nm. This implies that stress was generated at the SiO2/4H-SiC interface and accumulated in the SiO2region during the thermal oxidation process. We investigated the influence of annealing in NO on stress generation, while the calculated stresses suggested similar values. Thus, we conclude the NO post-annealing has no drastic effect on stress relaxation at an SiO2/4H-SiC interface.

Source:IOPscience
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Defect formation in 4H-SiC single crystal grown on the prismatic seeds

The defect structure of 4H silicon carbide single crystals grown by PVT method on three prismatic seeds (10-10), (11-20) and (8.3.-11.0) is considered. The only defects existing in the grown ingots are stacking faults and basal plane dislocations. The type of stacking fault is studied. The dependence of stacking fault morphology on the seed orientation is analyzed.

Source:IOPscience
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Growth and characterization of 3C–SiC and 2H–AlN/GaN films and devices produced on step-free 4H–SiC mesa substrates

While previously published experimental results have shown that the step-free (0 0 0 1) 4H–SiC mesa growth surface uniquely enables radical improvement of 3C–SiC and 2H–AlN/GaN heteroepitaxial film quality (>100-fold reduction in extended defect densities), important aspects of the step-free mesa heterofilm growth processes and resulting electronic device benefits remain to be more fully elucidated. This paper reviews and updates recent ongoing studies of 3C–SiC and 2H–AlN/GaN heteroepilayers grown on top of 4H–SiC mesas. For both 3C–SiC and AlN/GaN films nucleated on 4H–SiC mesas rendered completely free of atomic-scale surface steps, TEM studies reveal that relaxation of heterofilm strain arising from in-plane film/substrate lattice constant mismatch occurs in a remarkably benign manner that avoids formation of threading dislocations in the heteroepilayer. In particular, relaxation appears to occur via nucleation and inward lateral glide of near-interfacial dislocation half-loops from the mesa sidewalls. Preliminary studies of homojunction diodes implemented in 3C-SiC and AlN/GaN heterolayers demonstrate improved electrical performance compared with much more defective heterofilms grown on neighbouring stepped 4H–SiC mesas. Recombination-enhanced dislocation motion known to degrade forward-biased 4H–SiC bipolar diodes has been completely absent from our initial studies of 3C–SiC diodes, including diodes implemented on defective 3C–SiC heterolayers grown on stepped 4H–SiC mesas.

Source:IOPscience
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Photoelectric properties of p-β-FeSi2/n-4H-SiC heterojunction near-infrared photodiode

We give the first report on the experimental investigation of a p-β-FeSi2/n-4H-SiC heterojunction. A p-β-FeSi2/n-4H-SiC heterojunction near-infrared photodiode was fabricated on 4H-SiC substrate by magnetron sputtering and rapid thermal annealing (RTA). Sharp film—substrate interfaces were confirmed by scanning electron microscopy (SEM). The current density—voltage and photoresponse characteristics were measured. The measurements showed that the device exhibited good rectifying properties. The photocurrent density was about 1.82 mA/cm2 at a bias voltage of −1 V under illumination by a 5 mW, 1.31 μm laser, and the dark current density was approximately 0.537 mA/cm2. The detectivity was estimated to be 8.8 × 109 cmHz1/2/W at 1.31 μm. All of the measurements were made at room temperature. The results suggest that the p-β-FeSi2/n-4H-SiC heterojunctions can be used as near-infrared photodiodes that are applicable to optically-activated SiC-based devices.

Source:IOPscience
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