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Extended defects in wide-bandgap semiconductors have been widely investigated using techniques providing either spectroscopic or microscopic information. Nano-Fourier transform infrared spectroscopy (nano-FTIR) is a nondestructive characterization method combining FTIR with nanoscale spatial resolution (∼20 nm) and topographic information. Here, we demonstrate the capability of nano-FTIR for the characterization of extended defects in semiconductors by investigating an in-grown stacking fault (IGSF) present in a 4H-SiC epitaxial layer. We observe a local spectral shift of the mid-infrared near-field response, consistent with the identification of the defect stacking order as 3C-SiC (cubic) from comparative simulations based on the finite dipole model (FDM). This 3C-SiC IGSF contrasts with the more typical 8H-SiC IGSFs reported previously and is exemplary in showing that nanoscale spectroscopy with nano-FTIR can provide new insights into the properties of extended defects, the understanding of which is crucial for mitigating deleterious effects of such defects in alternative semiconductor materials and devices.

This study presents empirical validation of a simulated novel hybrid edge termination (HET) structure with planar ion implantation processing for vertical gallium nitride (GaN) diodes. The hybrid structure combines a junction termination extension (JTE) with superimposed guard rings (GRs), creating zones with alternating implantation depths. A design optimization strategy is employed to match the charge profile in the termination to that of a reference beveled edge termination, and is validated through the fabrication of ~1.5 kV GaN diodes. The breakdown voltage of the hybrid termination is tied to the fitting error between the charge profile of the hybrid structure and the reference bevel, as confirmed through simulations and experimental results. The proposed structure successfully emulates the properties of a bevel termination without the need for complex etching or lithography procedures. Additionally, the tolerance of the proposed hybrid structure to major process variations during the wafer growth and device fabrication are studied in simulations. The hybrid termination structure showcases remarkable robustness against major process variations, making it a viable choice for high-yield manufacturing. The findings and patterns presented in this work offer significant insights for the design and large-scale production of forthcoming high-power vertical GaN devices.

Foundry compatible vertical GaN PiN diodes were fabricated. The devices investigated in this work are based on 8 um drift layer thickness to achieve ∼1.2 kV of voltage blocking. Three different anode doping levels were fabricated on three wafers with the same p-layer thickness, and planar hybrid edge termination. The moderate anode doping level of 1 × 1018 cm−3has achieved the highest breakdown voltage of 1.2 kV and its temperature-dependent breakdown behavior proved an avalanche behavior. Furthermore, our electroluminescence displayed the breakdown at the edge of the anode. Our simulation results imply an improvement in the field management with moderate anode doping.

In this work, the effects of the substrate defect density and distribution on the reverse leakage behavior of GaN vertical Schottky diodes and p–i–n diodes are investigated. A direct connection between the reverse leakage behavior of GaN based vertical devices and the dislocation density of the underlying material was determined. The difference in the leakage current for devices on different locations of the wafer can be as high as 6 orders of magnitude (for p–i–n diodes) at −200V, for HVPE substrate with inhomogeneous but predictable defect distributions (GaN substrates with dot-core inversion domain features). For comparison, using HVPE substrates with uniform defect distribution (but with no cores), the p–i–n diodes show much more uniform leakage behavior, varying within only an order of magnitude, and that range fell within the much greater range of that for the inhomogeneous substrates. The substrates with inhomogeneous defect distribution proved to be useful to show the direct correlation. The topography measurements confirmed that the wafers with inhomogeneous defect distribution possess periodically patterned core-centers with higher defect density and larger lattice distortions surrounded by other regions, which have very low defect concentrations. Devices located away from the defective core-centers result in a reduction of the reverse bias leakage by over two orders of magnitude at −10 V for Schottky diodes. Similar trends are also observed in the p–i–n diodes; the devices close to the core centers show the highest reverse leakage (>0.01 A cm−2at −200V). Devices further away from the core-centers (lower dislocation density) show lower reverse leakage current. Moreover, the p–i–n diodes on regions more than 300 μm away from the core-centers show the best leakage behavior (<10−7A cm−2at −200V) of all the devices, outperforming the devices on the substrates with uniform defect distribution (∼10−6A cm−2at −200V). The results from this study show that the substrate defect density and distribution play important roles in the device leakage current. X-ray topography is extremely effective for studying defect characteristics underneath individual devices. The use of the wafers with inhomogeneous, but predictable defect density clearly demonstrated the importance of low defect densities for high device performance.

Vertical heterojunction p-CuI/n-Ga2O3diodes were fabricated on commercial ?-Ga2O3substrates using the reaction of epitaxially-sputtered Cu with natural I2vapor at room temperature followed by either a high temperature I2gas reaction or an I2solution treatment to remove iodine vacancies. Results show that using an epitaxially-oriented over a polycrystalline Cu layer produces larger and more strongly bonded CuI crystals. Hall and current-voltage measurements support rectifying behavior consistent with p-CuI/n-Ga2O3heterojunction characteristics including 8 orders of magnitude Ion/Ioffratio and an ideality factor of 1.37 measured on the sample with the lowest concentration of iodine vacancies.

A letter to the editor is presented in response to an article about the lack of safe and cost-effective methods of toxic waste disposal in the U.S. in the March 1, 1982 issue.