Band offsets in YSZ/InGaZnO4 heterostructure system.

The energy discontinuity in the valence band (deltaE(v)) of Y2O3-stabilized ZrO2 (YSZ)/InGaZnO4 (IGZO) heterostructures was obtained from X-ray photoelectron spectroscopy (XPS) measurements. The YSZ exhibited a bandgap of 4.4 eV from absorption measurements. A value of deltaE(v) = 0.57 +/- 0.12 eV was obtained by using Ga 2P3/2, Zn 2p3/2 and In 3d5/2 energy levels as references. This implies a conduction band offset (deltaE(c)) of 0.63 eV in YSZ/InGaZnO4 heterostructures and a nested interface band alignment.

Size-dependent electrical conductivity of indium zinc oxide deposited by RF magnetron sputtering.

We investigated the size-dependent electrical conductivities of indium zinc oxide stripes with different widths from 50 nm to 4 microm and with the same thickness of 50 nm deposited by RF magnetron sputtering. The size of the indium zinc oxide stripes was controlled by e-beam lithography. The distance of the two Ti/Au Ohmic electrodes along the indium zinc oxide stripes was kept constant at 25 microm. The electrical conductivity decreased as the size of the indium zinc oxide stripes decreased below a critical width (80 nm). The activation energy, derived from the electric conductivity versus temperature measurement, was dependent on the dimensions of indium zinc oxide stripes. These results can be understood as stemming from surface charge trapping from the absorption of oxygen and/or water vapor, which leads to an increase in the energy difference between the conduction energy band and the Fermi energy.

GaN, ZnO and InN nanowires and devices.

A brief review is given of recent developments in wide bandgap semiconductor nanowire synthesis and devices fabricated on these nanostructures. There is strong interest in these devices for applications in UV detection, gas sensors and transparent electronics.

Nanoscale magnetic regions formed in GaN implanted with Mn.

Platelet structures with diameters less than 250 A and hexagonal symmetry were formed in GaN by high dose Mn+ ion implantation and annealing at 700-1000 degrees C. Selected-area diffraction pattern analysis indicates that these regions are GaxMn1-xN with a different lattice constant to the host GaN. The presence of the GaMnN corresponds to ferromagnetic behavior of the samples with a Curie temperature of approximately 250 K.

Performance of AlGaN/GaN high electron mobility transistors at nanoscale gate lengths.

The DC and RF performance of AlGaN/GaN high electron mobility transistors with nanoscale gate lengths is presented. The layer structures were grown by either metal organic chemical vapor deposition or rf plasma-assisted molecular beam epitaxy. Excellent scaling properties were observed as a function of both gate length and width and confirm that these devices are well suited to both high speed switching and power microwave applications.

Unconventional carrier-mediated ferromagnetism above room temperature in ion-implanted (Ga, Mn)P:C.

Ion implantation of Mn ions into hole-doped GaP has been used to induce ferromagnetic behavior above room temperature for optimized Mn concentrations near 3 at. %. The magnetism is suppressed when the Mn dose is increased or decreased away from the 3 at. % value, or when n-type GaP substrates are used. At low temperatures the saturated moment is on the order of 1 Bohr magneton, and the spin wave stiffness inferred from the Bloch-law T(3/2) dependence of the magnetization provides an estimate T(c)=385 K of the Curie temperature that exceeds the experimental value, T(c)=270 K. The presence of ferromagnetic clusters and hysteresis to temperatures of at least 330 K is attributed to disorder and proximity to a metal-insulating transition.