Weak localization in compositionally graded Al<sub>x</sub>Ga<sub>1-x</sub>N

ORAL

Abstract

We report on the observation of weak localization in the compositionally graded AlxGa1-xN. The polar discontinuity at the epitaxial interface of dissimilar nitrides could introduce a two-dimensional electron gas. Compositionally graded structures, however, could introduce similar sheet carrier density distributed across the film. The various heterostructures were grown on AlN single crystal substrate using metal-organic chemical vapor deposition. The concentration of aluminum was graded, from x=0.56 to x=1, uniformly across the film thickness. The Hall resolved carrier density (1.35×1018 cm-3) closely matches the theory predicted values, hinting an extremely low density of compensating defects. Room temperature capacitance measurements reveal a three-dimensional distribution of charge carriers. The sheet resistance shows a metallic behavior (dRs/dT>0) with negligible Hall carrier freeze-out, cooling down to helium liquid temperature. Signatures of the weak localization were observed in the longitudinal magnetoresistance below 30 K. The magnetoresistance shows a well-known parabolic behavior at higher temperatures. The low-temperature longitudinal magnetoresistance shows good agreement a two-dimensional weak localization model, suggesting a dimensional crossover with temperature.

–

Presenters

  • Kaveh Ahadi

    • Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA

Authors

  • Abdullah Shafe

    • Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA

  • Athby Al-Tawhid

    • Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
    • North Carolina State University

  • Pegah Bagheri

    • Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA

  • Pramod Reddy

    • Adroit Materials Inc., 2054 Kildaire Farm Road, Suite 205, Cary, NC 27518, USA
    • Adroit Materials, Inc.

  • Seiji Mita

    • Adroit Materials Inc., 2054 Kildaire Farm Road, Suite 205, Cary, NC 27518, USA
    • Adroit Materials, Inc.

  • Baxter Moody

    • Adroit Materials Inc., 2054 Kildaire Farm Road, Suite 205, Cary, NC 27518, USA

  • Ramon Collazo

    • Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA
    • North Carolina State University
    • Materials Science and Engineering, North Carolina State University

  • Zlatko Sitar

    • Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA
    • North Carolina State University
    • Materials Science and Engineering, North Carolina State University

  • Kaveh Ahadi

    • Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA