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We present the electrical characterization of N-polar AlN layers grown by metal-organic vapor phase epitaxy and the demonstration of N-polar AlN-channel metal-semiconductor field-effect transistors (MESFETs). A high concentration of silicon is unintentionally incorporated during the high-temperature growth of N-polar AlN, causing high buffer leak current. The silicon concentration reduces from 2x10^18 /cm^3 to 9x10^15 /cm^3 with decreasing growth temperature, reducing the buffer leak current to 5.6 nA/mm at a 100 V bias. The N-polar AlN MESFET exhibits an off-state drain current of 0.27 nA/mm and a transistor on/off ratio of 4.6x10^4 due to the high-resistivity AlN buffer layers., Comment: This is the version of the article before peer review or editing, as submitted by an author to Applied Physics Express. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.7567/APEX.11.101002

We present a comprehensive study on metal-organic vapor phase epitaxy growth of N-polar and Al-polar AlN on 4H-SiC with 4 deg miscut using constant growth parameters. At a high temperature of 1165 degC, N-polar AlN layers had high crystalline quality whereas the Al-polar AlN surfaces had a high density of etch pits. For N-polar AlN, the V/III ratio below 1000 forms hexagonal hillocks, while the V/III ratio over 1000 yields step bunching without the hillocks. 1-um-thick N-polar AlN layer grown in optimal conditions exhibited FWHMs of 307, 330 and 337 arcsec for (002), (102) and (201) reflections, respectively.

We present the effect of miscut angle of SiC substrates on N-polar AlN growth. The N-polar AlN layers were grown on C-face 4H-SiC substrates with a miscut towards <-1100> by metal-organic vapor phase epitaxy (MOVPE). The optimal V/III ratios for high-quality AlN growth on 1 deg and 4 deg miscut substrates were found to be 20000 and 1000, respectively. MOVPE grown N-polar AlN layer without hexagonal hillocks or step bunching was achieved using a 4H-SiC substrate with an intentional miscut of 1 deg towards <-1100>. The 200-nm-thick AlN layer exhibited X-ray rocking curve full width half maximums of 203 arcsec and 389 arcsec for (002) and (102) reflections, respectively. The root mean square roughness was 0.43 nm for a 2 um x 2 um atomic force microscope scan.

We propose a new generalized-ensemble algorithm, which we refer to as the multibaric-multithermal Monte Carlo method. The multibaric-multithermal Monte Carlo simulations perform random walks widely both in volume space and in potential energy space. From only one simulation run, one can calculate isobaric-isothermal-ensemble averages at any pressure and any temperature. We test the effectiveness of this algorithm by applying it to the Lennard-Jones 12-6 potential system with 500 particles. It is found that a single simulation of the new method indeed gives accurate average quantities in isobaric-isothermal ensemble for a wide range of pressure and temperature., Comment: 8 pages, (RevTeX), 5 figures

Phenomenological equations describing the Seebeck, Hall, Nernst, Peltier, Ettingshausen, and Righi-Leduc effects are numerically solved for the temperature, electric current, and electrochemical potential distributions of semiconductors under magnetic field. The results are compared to experiments., Comment: 4 pages, 7 figures. Submitted to Proceedings of XVII International Conference on Thermoelectrics (ICT98), 1998 Nagoya, Japan