Using site-specific plan-view transmission electron microscopy (TEM) and light emission imaging, we have identified stacking faults formed during forward biasing of 4H-SiC p-i-n diodes. These stacking faults (SFs) are bounded by Shockley partial dislocations and are formed by shear strain rather than by the condensation of vacancies or interstitials. Detailed analysis using TEM diffraction contrast experiments reveal SFs with leading carbon-core Shockley partial dislocations as well as with the silicon-core partial dislocations observed in plastic deformation of 4H-SiC at elevated temperatures. The leading Shockley partials are seen to relieve both tensile and compressive strain during p-i-n diode operation, suggesting the presence of a complex inhomogeneous strain field in the 4H-SiC layer.

We report on AlGaN∕GaN heterojunction structures for use in Hall effect sensors working over a wide range of temperatures. Room temperature current-related magnetic sensitivity of 55V∕AT at a sheet resistance below 300Ω∕sq and very low temperature cross sensitivity of 103ppm∕°C up to 300°C were obtained for a square-shaped Hall effect sensor. The active layer of the Hall effect sensor is the two-dimensional electron gas formed at the Al0.3Ga0.7N and GaN heterointerface caused by the gradient in the total polarization between the AlGaN barrier and the GaN buffer layer, which results in the positive polarization induced interface charge attracting free electrons. The temperature-dependent transport properties of the heterojunction were analyzed by Hall measurement. The drop of its electron mobility from room temperature to 300°C is mainly due to the enhanced polar optical scattering, while the very stable sheet carrier density contributes to the excellent temperature cross sensitivity of the Hall effect sensor.

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Articles you may be interested inLattice mismatch and crystallographic tilt induced by high-dose ion-implantation into 4H-SiC Effects of implantation temperature on damage accumulation in Al-implanted 4H-SiC J. Appl. Phys. 95, 4012 (2004); 10.1063/1.1666974 High-energy (MeV) Al and B ion implantations into 4H-SiC and fabrication of pin diodes Comparison of the annealing behavior of high-dose nitrogen-, aluminum-, and boron-implanted 4H-SiC Appl.Multiple energy N ͑at 500°C͒ and Al ͑at 800°C͒ ion implantations were performed into bulk semi-insulating 4H-SiC at various doses to obtain uniform implant concentrations in the range 1 ϫ10 18 -1ϫ10 20 cm Ϫ3 to a depth of 1.0 m. Implant anneals were performed at 1400, 1500, and 1600°C for 15 min. For both N and Al implants, the carrier concentration measured at room temperature for implant concentrations р10 19 cm Ϫ3 is limited by carrier ionization energies, whereas for the 10 20 cm Ϫ3 implant, the carrier concentration is also limited by factors such as the solubility limit of the implanted nitrogen and residual implant damage. Lattice quality of the as-implanted and annealed material was evaluated by Rutherford backscattering spectroscopy measurements. Residual lattice damage was observed in the implanted material even after high temperature annealing. Atomic force microscopy revealed increasing deterioration in surface morphology ͑due to the evaporation of Si containing species͒ with increasing annealing temperature. The surface damage is in the form of long furrows running in one direction across the wafer to a depth of ϳ25 nm from the surface for samples annealed at 1600°C for 15 min. We measured room temperature sheet resistivities of ϳ70 and 1.2ϫ10 4 ⍀/sq., respectively, for 2ϫ10 19 cm Ϫ3 N ͑1500°C annealing͒ and 1ϫ10 20 cm Ϫ3 Al ͑1600°C annealing͒ implanted samples.