Papers by Keyword: Breakdown Field

Abstract: This study investigates the role of the electrical failure of the SiO₂ film in the breakdown of SiO₂/ZrO₂ and SiO₂/HfO₂ stacks. Our findings indicate that the breakdown is governed by the SiO₂ film, regardless of its thickness. This highlights the importance of carefully considering the interfacial SiO₂ layer when using high-k materials in SiC devices. We demonstrate that thicker SiO₂ layers offer several benefits, including reduced leakage, enhanced thermal stability and electrical strength, and decreased trapping. In contrast, stacks with thinner SiO₂ have a higher effective k value, exploiting the benefits of high-k dielectrics. Our experimental results suggest that a 7 nm SiO₂ layer underlying 30 nm crystalline ZrO₂ or HfO₂ provides optimal performance. Furthermore, we present calculations that reveal the trade-off between SiO₂ thickness, k value, and breakdown voltage for a 50 nm thick dielectric stack. Our results imply that a k value exceeding 20 does not yield significant benefits in 50 nm thick SiO₂/dielectric stacks.

Abstract: We investigated the electrical and structural effects of silicon (Si), yttrium (Y) and lanthanum (La) doping in 10-45 nm thick hafnium dioxide (HfO₂) films on silicon carbide (SiC) and Si substrates. We show that the introduction of Si dopants leads to a significant enhancement of the electric breakdown field and a reduction of the leakage current density by elevating the crystallization temperature. This effect becomes stronger with higher Si content. In contrast, Y and La doping does not raise T_C but increases the tetragonal and orthorhombic phase portion within the crystalline films and therefore enhances the dielectric constant k. Furthermore, we show that larger grains in crystalline films are associated with a higher leakage current density.

Abstract: Modeling and simulation of 3C-SiC power devices such as MOSFETs and diodes requires a model for the breakdown field that is consistent with the Monte-Carlo-simulated ionization rates of electron and holes and supported by experimental results. The challenge one faces is the limited number of publications reporting such calculations and the limited availability of high-quality ionization breakdown data for 3C-SiC diodes. We therefore performed a series of 2D simulations of both n-type and p-type Schottky diodes and p⁺-n diodes that confirms the general breakdown field trend with doping density obtained from experiments. We uncovered a difference between n-type and p-type diode breakdown behavior, identified the discrepancy between the calculations and the experimental data, and extracted a simple breakdown field model, useful for further 3C-SiC device design and simulation.

Abstract: An extensive study on the use of Si as a substrate for the growth of AlGaN/GaN layers for High-Electron-Mobility Transistor (HEMT) were studied and reported in this article. We have used thick buffers to grow high resistive i-GaN by MOCVD which offers a high breakdown voltage. While the leakage through buffer and substrate can be controlled by thick buffer, the leakage through gate is controlled using a thin 2-nm in-situ grown i-GaN cap layer. We have evidenced a high figure of merit (BV²/R_ON) of 2.6 x 10⁸ V²Ω^-1cm^-2 for AlGaN/GaN HEMTs grown on 4-inch Si substrate. The challenges before the MOCVD growth of GaN on Si is also discussed in detail.

Abstract: This paper reports on initial fabrication and electrical characterization of 3C-SiC p+n junction diodes grown on step-free 4H-SiC mesas. Diodes with n-blocking-layer doping ranging from ~ 2 x 1016 cm-3 to ~ 5 x 1017 cm-3 were fabricated and tested. No optimization of junction edge termination or ohmic contacts was employed. Room temperature reverse characteristics of the best devices show excellent low-leakage behavior, below previous 3C-SiC devices produced by other growth techniques, until the onset of a sharp breakdown knee. The resulting estimated breakdown field of 3C-SiC is at least twice the breakdown field of silicon, but is only around half the breakdown field of <0001> 4H-SiC for the doping range studied. Initial high current stressing of 3C diodes at 100 A/cm2 for more than 20 hours resulted in less than 50 mV change in ~ 3 V forward voltage.