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1. Schottky contacts to N-polar GaN with SiN interlayer for elevated temperature operation

   https://doi.org/10.1063/5.0083588  

   Khachariya, Dolar; Szymanski, Dennis; Reddy, Pramod; Kohn, Erhard; Sitar, Zlatko; Collazo, Ramón; Pavlidis, Spyridon (April 2022, Applied Physics Letters)

   In this Letter, we unveil the high-temperature limits of N-polar GaN Schottky contacts enhanced by a low-pressure chemical vapor deposited (LPCVD) SiN interlayer. Compared to conventional Schottky diodes, the insertion of a 5 nm SiN lossy dielectric interlayer in-between Ni and N-polar GaN increases the turn-on voltage ( V ON ) from 0.4 to 0.9 V and the barrier height ( ϕ B ) from 0.4 to 0.8 eV. This modification also reduces the leakage current at zero bias significantly: at room temperature, the leakage current in the conventional Schottky diode is >10 3 larger than that observed in the device with the SiN interlayer, while at 200 °C, this ratio increases to 10 5 . Thus, the rectification ratio (I ON /I OFF ) at ±1.5 V reduces to less than one at 250 °C for the conventional Schottky diode, whereas for SiN-coated diodes, rectification continues until 500 °C. The I–V characteristics of the diode with an SiN interlayer can be recovered after exposure to 400 °C or lower. Contact degradation occurs at 500 °C, although devices are not destroyed yet. Here, we report N-polar GaN Schottky contact operation up to 500 °C using an LPCVD SiN interlayer. 

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2. Structural and electronic properties of NbN/GaN junctions grown by molecular beam epitaxy

   https://doi.org/10.1063/5.0083184  

   Wright, John G.; Chang, Celesta S.; Muller, David A.; Xing, Huili G.; Jena, Debdeep (May 2022, APL Materials)

   We report the structural and electronic properties of NbN/GaN junctions grown by plasma-assisted molecular beam epitaxy. High crystal-quality NbN films grown on GaN exhibit superconducting critical temperatures in excess of 10 K for thicknesses as low as 3 nm. We observe that the NbN lattice adopts the stacking sequence of the underlying GaN and that domain boundaries in the NbN thereby occur at the site of atomic steps in the GaN surface. The electronic properties of the NbN/GaN junction are characterized using Schottky barrier diodes. Current–voltage–temperature and capacitance–voltage measurements are used to determine the Schottky barrier height of the NbN/GaN junction, which we conclude is ∼1.3 eV. 

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3. Vertical GaN junction barrier Schottky diodes with near-ideal performance using Mg implantation activated by ultra-high-pressure annealing

   https://doi.org/10.35848/1882-0786/ac8f81  

   Khachariya, Dolar; Stein, Shane; Mecouch, Will; Breckenridge, M. Hayden; Rathkanthiwar, Shashwat; Mita, Seiji; Moody, Baxter; Reddy, Pramod; Tweedie, James; Kirste, Ronny; et al (September 2022, Applied Physics Express)

   Abstract We report a kV class, low ON-resistance, vertical GaN junction barrier Schottky (JBS) diode with selective-area p-regions formed via Mg implantation followed by high-temperature, ultra-high pressure (UHP) post-implantation activation anneal. The JBS has an ideality factor of 1.03, a turn-on voltage of 0.75 V, and a specific differential ON-resistance of 0.6 mΩ·cm 2 . The breakdown voltage of the JBS diode is 915 V, corresponding to a maximum electric field of 3.3 MV cm −1 . These results underline that high-performance GaN JBS can be realized using Mg implantation and high-temperature UHP post-activation anneal. 

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4. A back-to-back diode model applied to van der Waals Schottky diodes

   https://doi.org/10.1088/1361-648X/ad69ef  

   Cloninger, Jeffrey_A; Harris, Raine; Haley, Kristine_L; Sterbentz, Randy_M; Taniguchi, Takashi; Watanabe, Kenji; Island, Joshua_O (August 2024, Journal of Physics: Condensed Matter)

   Abstract The use of metal and semimetal van der Waals contacts for 2D semiconducting devices has led to remarkable device optimizations. In comparison with conventional thin-film metal deposition, a reduction in Fermi level pinning at the contact interface for van der Waals contacts results in, generally, lower contact resistances and higher mobilities. Van der Waals contacts also lead to Schottky barriers that follow the Schottky–Mott rule, allowing barrier estimates on material properties alone. In this study, we present a double Schottky barrier model and apply it to a barrier tunable all van der Waals transistor. In a molybdenum disulfide (MoS₂) transistor with graphene and few-layer graphene contacts, we find that the model can be applied to extract Schottky barrier heights that agree with the Schottky–Mott rule from simple two-terminal current–voltage measurements at room temperature. Furthermore, we show tunability of the Schottky barrierin-situusing a regional contact gate. Our results highlight the utility of a basic back-to-back diode model in extracting device characteristics in all van der Waals transistors. 

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5. Demonstration of near-ideal Schottky contacts to Si-doped AlN

   https://doi.org/10.1063/5.0174524  

   Quiñones, C. E.; Khachariya, D.; Bagheri, P.; Reddy, P.; Mita, S.; Kirste, R.; Rathkanthiwar, S.; Tweedie, J.; Pavlidis, S.; Kohn, E.; et al (October 2023, Applied Physics Letters)

   Near-ideal behavior in Schottky contacts to Si-doped AlN was observed as evidenced by a low ideality factor of 1.5 at room temperature. A temperature-independent Schottky barrier height of 1.9 eV was extracted from temperature-dependent I–V measurements. An activation energy of ∼300 meV was observed in the series resistance, which corresponded to the ionization energy of the deep Si donor state. Both Ohmic and Schottky contacts were stable up to 650 °C, with around four orders of magnitude rectification at this elevated temperature. These results demonstrate the potential of AlN as a platform for power devices capable of operating in extreme environments. 

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