Dresden 2003 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 14: Poster I

HL 14.92: Poster

Montag, 24. März 2003, 17:00–19:30, HSZ/P2

Electrical Conduction of AlGaN/GaN 2DEG Heterostructures grown on Si(111) — •M. Kočan¹, M. Bertelli¹, E. Donà¹, A. Rizzi², and H. Lüth¹ — ¹ISG1, Forschungszentrum Jülich GmbH, D-52078 Jülich, Germany — ²IV. Physikalisches Inst., Georg-August-Universität Göttingen, D-37073 Göttingen, Germany

AlGaN/GaN two dimensional electron gas (2DEG) heterostructures on Si(111) were grown by plasma assisted Molecular Beam Epitaxy. The growth process was optimized concerning surface morphology and structural quality. A significant improvement was achieved by growing an Al_0.4Ga_0.6N interlayer (100 nm of thickness) on top of the AlN nucleation layer before growth of the 1µm thick GaN layer. Temperature dependent Hall-effect experiments of GaN(cap, 8nm)/Al_0.25Ga_0.75N(25nm)/GaN(1µm) heterostructures show a complex behavior, whereby both n-type (below 35 K) and p-type (above 35 K) conductivity is observed. Self consistent Schrödinger-Poisson one dimensional band scheme calculations point out the formation of several conductivity channels in the grown structure. Due to the polarization charges at the GaN/AlGaN/AlN/Si(111) interfaces in the buffer-nucleation layer region, two dimensional hole gases (2DHGs) are formed, with concentrations comparable to that of the 2DEG on top[1]. At lower temperatures, once the conductivity of the 1µm thick GaN layer can be assumed to be frozen out, only the n-type conductivity of the 2DEG in the active region contributes to the Hall effect.

[1] M. Kočan et al., phys. stat. sol (c) 0, No. 1, 196 (2002)