Weak antilocalization in a polarization-doped AlxGa1-xN/GaN heterostructure with single subband occupation

Spin-orbit scattering in a polarization-doped Al0.30Ga0.70N/GaN two-dimensional electron gas with one occupied subband is studied at low temperatures. At low magnetic fields weak antilocalization is observed, which proves that spin-orbit scattering occurs in the two-dimensional electron gas. From measurements at various temperatures the elastic scattering time tau(tr), the dephasing time tau(phi), and the spin-orbit scattering time tau(so) are extracted. Measurements in tilted magnetic fields were performed, in order to separate spin and orbital effects

The State of Strain in Single GaN Nanocolumns As Derived from Micro-Photoluminescence Measurements

In the present paper, studies on the state of strain in single and ensembles of nanocolumns investigated by photoluminescence spectroscopy will be presented. The GaN nanocolumns were either grown in a bottom-up approach or prepared in a top-down approach by etching compact GaN layers grown on Si(111) and sapphire (0001) substrates. Experimental evidence for strain relaxation of the nanocolumns was found. The difference and development of the strain value for different nanocolumns could be verified by spatially resolved micro-photoluminescence on single nanocolumns separated from their substrate. A common D0X spectral position at 3.473 eV was found for all separated single GaN nanocolumns independent of the substrate or processing technique used, as expected for a relaxed system

Spin-orbit coupling in gated AlGaN/GaN 2-dimensional electron gases

Weak antilocalization was studied in an Alx Ga1-x N/GaN two-dimensional electron gas as a function of temperature for various gate voltages. By fitting the weak antilocalization measurements by a theoretical model we found that the spin-orbit scattering length does not vary upon changing the carrier concentration or the temperature. The occurrence of spin-orbit coupling was attributed to the crystal inversion asymmetry. The presence of beating patterns observed in the Shubnikov-de Haas oscillations were not assigned to the presence of spin-orbit coupling but rather to structural inhomogeneities in the Alx Ga1-x N/GaN crystal

Weak antilocalization in gate-controlled Al/sub x/Ga/sub 1-x/N/GaN two-dimensional electron gases

Weak antilocalization and the Shubnikov-de Haas effect were investigated in AlxGa1-xN/GaN two-dimensional electron gases. The weak antilocalization measurements on a gated sample revealed a constant spin-orbit scattering length, which does not change if the Al content or the thickness of the AlxGa1-xN barrier layer is varied. The occurrence of spin-orbit coupling is assigned to the lack of crystal inversion symmetry. Although for some of the samples a beating pattern was observed in the Shubnikov-de Haas oscillations, its presence was not attributed to spin-orbit coupling but rather to inhomogeneities in the AlxGa1-xN barrier