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HL: Fachverband Halbleiterphysik

HL 50: Invited Talk Schmult

HL 50.1: Invited Talk

Friday, March 30, 2007, 10:15–11:00, H15

Quantum Transport in High Mobility GaN/AlGaN 2DEGs and Nanostructures — •Stefan Schmult¹, Alexander Punnoose¹, Michael J. Manfra¹, Hungtao Chou², David Goldhaber-Gordon², and Richard J. Molnar³ — ¹Bell Labs, Alcatel-Lucent, Murray Hill, NJ, USA — ²Stanford University, Stanford, CA, USA — ³MIT Lincoln Lab, Lexington, MA, USA

We report on the transport properties of high mobility GaN/AlGaN two-dimensional electron gases (2DEGs) grown by molecular beam epitaxy. Using an insulated gate Hall bar structure, the electron density is continuously tuned from 2×10¹²cm⁻² down to 2×10¹¹cm⁻². At T=0.3K, the 2DEG displays a maximum mobility of 1.67×10⁵cm²/Vs at a sheet density of 9.1×10¹¹cm⁻². Detailed analysis of the dependence of mobility on 2D density allows us to isolate the primary scattering mechanisms at low carrier density and low temperatures. A detailed study of the weak localization and antilocalization corrections to the classical conductivity identifies that the spin-orbit coupling is of Bychkov-Rashba type. We estimate the values of the coupling constant and the spin relaxation time and find that spin-orbit scattering is not negligible as one might expect for a wide-bandgap material. Recently we have realized electron transport through quantum point contacts (QPCs) and quantum dots (QDs) in GaN/AlGaN nanostructures. True one-dimensional conduction channels in QPCs show well quantized plateaus, which spin-split in high perpendicular magnetic field. The transconductance of a QD depends on its size and exhibits Coulomb oscillations, representing resonant transport through the dot.