The authors demonstrate the impact of growth kinetics on the surface and structural properties of N-face InN grown by molecular beam epitaxy. Superior surface morphology with step-flow growth features is achieved consistently under In-rich conditions in a low-temperature region of 500-540 degrees C. Remarkably, off-axis x-ray rocking curve (omega scans) widths are found to be independent of the growth conditions. The band gap determined from optical absorption measurements of optimized InN is 0.651 eV, while photoluminescence peak emission occurs at even lower energies of similar to 0.626 eV. Hall measurements show room temperature peak electron mobilities as high as 2370 cm(2)/V s at a carrier concentration in the low 10(17) cm(-3) region. Analysis of the thickness dependence of the carrier concentration demonstrates a n-type surface accumulation layer with a sheet carrier concentration of similar to 3x10(13) cm(-2). (c) 2006 American Institute of Physics.

The authors report on the excitation wavelength dependence of terahertz emission from n-InN and bulk p-InAs pumped with femtosecond pulses tunable from 800 to 1500 nm. The terahertz amplitude, normalized to pump and probe power, from both narrow band gap semiconductors remains relatively constant over the excitation wavelength range. In addition, terahertz radiation from In- and N-face InN samples with bulk carrier concentrations ranging from 10(17) to 10(19) cm(-3) is also investigated, showing a strong dependence of terahertz emission on bulk carrier concentration. The experimental results agree well with calculations based on drift-diffusion equations incorporating momentum conservation and relaxation. (c) 2006 American Institute of Physics.

We study the effect of different deposition conditions on the properties of In-polar InN grown by plasma-assisted molecular beam epitaxy. GaN buffer layers grown in the Ga-droplet regime prior to the InN deposition significantly improved the surface morphology of InN films grown with excess In flux. Using this approach, In-polar InN films have been realized with room temperature electron mobilities as high as 2250 cm(2)/V s. We correlate electron concentrations in our InN films with the unintentionally incorporated impurities, oxygen and hydrogen. A surface electron accumulation layer of 5.11x10(13) cm(-2) is measured for In-polar InN. Analysis of optical absorption data provides a band gap energy of similar to 0.65 eV for the thickest InN films. (c) 2006 American Institute of Physics.