ANISOTROPIC TRANSPORT-PROPERTIES OF THE 2-DIMENSIONAL ELECTRON-GAS IN ORDERED-DISORDERED GAINP2 HOMOJUNCTIONS - THE STRUCTURE OF ORDERED DOMAINS

The modulation-doped ordered-GaInP2/disordered-GaInP2 homojunction is presented. Capacitance-voltage (CV) profiling techniques, temperature-dependent Hall and resistivity measurements, cross-sectional transverse electron micrographs (TEM), and high-field magnetotransport have been used to characterize this structure grown by metal-organic vapor-phase epitaxy. The CV measurements showed a narrow profile at the homointerface with an order of magnitude reduction in carrier density within 3 nm. Typical two-dimensional behavior was observed from Hall data showing sheet carrier densities as high as 3.6×1013 cm-2 without carrier freeze-out, and constant mobilities around 900 cm2 V-1 s-1 below T=100 K. The 300-K channel conductivity of this junction is 3.2×10-3 Ω-1, which is higher than reported for other two-dimensional electron gases. By proper choice of the substrate orientation, domains of only the (111̄) ordering variant were present. TEM showed elongated shapes of average thickness 3.5-6 nm and length 75 nm in the (011) plane. By using Hall bars with different current directions, an asymmetry is observed for the contributions to the scattering mechanisms which determine the mobility: ''mesoscopic'' interface-roughness scattering for T<100 K and cluster scattering for 100<T<300 K. Polar optical scattering at T>300 K indicates strong electron-phonon coupling. This asymmetry shows that the domain length in the (011) plane is larger than that in the (011̄) plane. The magnetoresistance ρxx and the Hall resistance ρxy show oscillations in reciprocal magnetic field involving an excited subband i with n2Di=7.6×1011 cm-2, where 2D denotes two dimensional. The ρxy versus B curve shows features of a slight parallel conduction. © 1994 The American Physical Society.