Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN/GaN heterostructures

Journal of Applied Physics - Tập 85 Số 6 - Trang 3222-3233 - 1999
O. Ambacher1, J. Smart1, R. Leoni1, Nils Weimann1, K. Chu1, Michael J. Murphy1, W. J. Schaff1, L.F. Eastman1, R. Dimitrov2, L.L. Wittmer2, M. Stutzmann2, W. Rieger3, J. Hilsenbeck3
1School of Electrical Engineering, Cornell University, Ithaca, New York 14853
2Walter Schottky Institute, TU-Munich, Am Coulombwall, 85748 Garching, Germany
3Ferdinand Braun Institute, Rudower Chaussee 5, 12489 Berlin, Germany

Tóm tắt

Carrier concentration profiles of two-dimensional electron gases are investigated in wurtzite, Ga-face AlxGa1−xN/GaN/AlxGa1−xN and N-face GaN/AlxGa1−xN/GaN heterostructures used for the fabrication of field effect transistors. Analysis of the measured electron distributions in heterostructures with AlGaN barrier layers of different Al concentrations (0.15<x<0.5) and thickness between 20 and 65 nm demonstrate the important role of spontaneous and piezoelectric polarization on the carrier confinement at GaN/AlGaN and AlGaN/GaN interfaces. Characterization of the electrical properties of nominally undoped transistor structures reveals the presence of high sheet carrier concentrations, increasing from 6×1012 to 2×1013 cm−2 in the GaN channel with increasing Al-concentration from x=0.15 to 0.31. The observed high sheet carrier concentrations and strong confinement at specific interfaces of the N- and Ga-face pseudomorphic grown heterostructures can be explained as a consequence of interface charges induced by piezoelectric and spontaneous polarization effects.

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Thông tin xuất bản

Journal of Applied Physics

Tập 85 Số 6

3222-3233

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