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Gold Schottky contacts to n-AlGaN were fabricated, and the influence of the semiconductor surface preparation on the electrical performance of the diodes was examined. More significantly, the electrical characteristics of the diodes were found to be sensitive to the environment in which they were exposed. Diodes stored in vacuum had stable but poor electrical characteristics, exhibiting the same high reverse leakage currents, low barrier heights, and high ideality factors as the freshly prepared diodes. On the other hand, didoes exposed to air changed over the course of days, in some cases with decreases in the reverse leakage currents by four or more orders of magnitude and increases in the barrier height by 0.3-0.5 eV. Further study of this change in electrical properties showed that the effect was reversible with exposure to N[sub 2] gas or vacuum and adequate temperature. In addition, the effect was more pronounced when the metal contact was thin, indicating that diffusion of gases through the metal was significant. This study suggests that nitride semiconductor devices with Schottky barriers to n-AlGaN as components may exhibit improved performance if they are initially stored in air for a few days prior to encapsulation and will also exhibit a pronounced sensitivity to their storage and operational environment if not adequately protected from it. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effects of negative polarization charge at the n-InGaN/p-GaN interface on the performance of hydride vapor phase-epitaxy deposited single heterostructure n-InGaN/p-GaN LEDs with p-side down are investigated. The strong peak emission wavelength blueshift and concomitant superlinear increase in light output as the injection current increases below 25 A/cm2 are characteristic of radiative tunneling. We show that the combination of two-dimensional hole gas formation on the n-InGaN side of the heterointerface and enhancement of the electron barrier to transport across this interface results in only ∼10% efficiency droop up to 500 A/cm2 without implementation of an AlGaN electron-blocking layer or a second heterointerface. [ABSTRACT FROM AUTHOR]

We report in situ doping of GaN with the rare earth element Nd by plasma-assisted molecular beam epitaxy. For the highest Nd effusion cell temperatures, Rutherford backscattering and secondary ion mass spectroscopy data indicate ∼5 at. % Nd in epilayers grown on c-plane sapphire. X-ray diffraction found no evidence of phase segregation under nitrogen-rich conditions with up to ∼1 at. % Nd, with the highest luminescence intensities corresponding to doping of ∼0.5 at. %. Spectral correlation of the Nd emission multiplets for above (325 nm) and below (836 nm) GaN bandgap excitations implies enhanced substitutional doping at the Ga site. [ABSTRACT FROM AUTHOR]

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 °C. Remarkably, off-axis x-ray rocking curve (ω 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 ∼0.626 eV. Hall measurements show room temperature peak electron mobilities as high as 2370 cm2/V s at a carrier concentration in the low 1017 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 ∼3×1013 cm-2. [ABSTRACT FROM AUTHOR]

Ni films on (0001) and ([formula]) InN exhibited different reaction kinetics upon annealing at 673K. Structural and chemical analysis using grazing incidence X-ray diffraction, transmission electron microscopy, and X-ray energy dispersive spectrometry indicated that an interfacial reaction did not occur between the Ni film and the In-polar (0001) InN layer. However, the N-polar face reacted with Ni to form the Ni3InNx ternary phase with an anti-perovskite structure. The difference in reactivity for Ni on In-face and N-face InN indicates that polarity alters the reaction and may also affect interactions between other metals and group III-nitride semiconductors. [ABSTRACT FROM AUTHOR]