Optical Detection of 2DEG in GaN/AlGaN Structures - High Magnetic Field Studies

Barbara Chwalisz 5A Wysmolek 5Roman Stepniewski 5Marek Potemski 2W Knap 3Jacek Baranowski 5Nicolas GRANDJEAN 4J Massies 4Paweł Prystawko 1Izabella Grzegory 1

1. Polish Academy of Sciences, High Pressure Research Center (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland
2. Grenoble High Magnetic Field Laboratory, MPI/FKF-CNRS (GHMFL), 25, Avenue des Martyrs, Grenoble 38-042, France
3. Groupe d'Etude des Semiconducteurs, CNRS-UMR 5650, Universite de Montpellier 2, 12 Place Eugene Bataillon, Montpellier 24095, France
4. CRHEA-CNRS, rue B. Gregory, Sophia Antipolis, 06560 Valbonne, France, France
5. Warsaw University, Institute of Experimental Physics (IEP UW), Hoża 69, Warszawa 00-681, Poland


Photoluminescence (PL) studies of the GaN/AlGaN structure are presented. PL spectra measured in magnetic fields up to 28T show periodic intensity oscillations, what is interpreted as a fingerprint of 2DEG confined at GaN/AlGaN interface.
The investigated structure was grown by molecular beam epitaxy (MBE) using highpressure bulk GaN as a substrate. The complete structure consisted of 2nm GaN quantum well (QW) embedded in the Al0.08Ga0.92N barriers grown on top of a thick GaN buffer layer.
Low temperature PL spectrum of the structure is dominated by the emission from the QW observed at 3.53 eV followed by sharp luminescence lines due to free and bound excitons originating from the GaN buffer layer.
In addition, in the energy range 3.40 - 3.45 eV of the PL spectrum, pronounced but relatively broad emission structure is observed. It shows typical temperature and excitation power dependencies as expected for 2DEG at GaN/AlGaN interface [1-3]. This identification is confirmed by the observation of intensity oscillations in magnetic field. They are direct consequence of 2DEG Landau quantization and the Fermi level oscillations. This observation allows us to determine the electron concentration present at the GaN/AlGaN interface. The obtained result is in good agreement with the value expected for this structure [4].
Surprisingly, it was observed that magneto-PL intensity oscillates also in other energy regions of the spectra. Appearance of these oscillations is discussed in terms of magnetic field induced potential redistribution and interactions between different layers existing in the structure.

[1] J. P. Bergman, et al. Appl. Phys. Lett. 69 (23), 3456 (1996)
[2] B. Shen, et al. Appl. Phys. Lett. 76 (6), 679 (2000)
[3] G. Martinez-Criado, et al. Mat. & Science Eng. B82, 200 (2001)
[4] O. Ambacher, et al. J. Phys. Cond. Matter 14 (13), 3399 (2002)

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Presentation: oral at E-MRS Fall Meeting 2003, Symposium A, by Barbara Chwalisz
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-26 13:13
Revised:   2009-06-08 12:55
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