GaN Schottky diodes were exposed to N2 or H2 Inductively Coupled Plasmas prior to deposition of the rectifying contact. Subsequent annealing, wet photochemical etching or (NH&S surface passivation treatments were examined for their effect on diode currentvoltage characteristics. We found that either annealing at 750 'C under N2, or removal of -500-600 A of the surface essentially restored the initial I-V characteristics. There was no measurable improvement in the plasma-exposed diode behavior with (NH&S treatments. 1 DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document.GaN-based devices are being developed for two basic classes of applications, namely blue/green/UV emitters and high power/high temperature electr~nics.(''~) The high bond energy, 8.92 eV/atom, of GaN has necessitated use of dry etching technologies for device patterning. Plasma induced damage to GaN may take several forms, all of which lead to changes in its electrical and optical properties, as follows:1. Ion induced creation of lattice defects which generally behave as deep level states and thus produce compensation, trapping or recombination in the material. Due to channeling of the low energy ions that strike the sample, and rapid diffusion of the defects created, the effects can be measured as deep as 1000 surface, even though the projected range of the ions is only 110 A. to 10l8 cme3. In the PL spectrum an intense broad band appeared at 3.05 eV, and there was an increase in intensity of the yellow band at 2.20 eV. The latter is thought to involve defects such as Ga, in some models. Use of Ar+/N2+ ion beams produced less degradation of both optical and electrical properties.Saotome at studied the effects of RIBEECR etching with pure Cl2 on GaN properties. Etch rates up to -1000 A-min-' at 500 V beam voltage were obtained. He-Cd (325 nm) laser irradiation was used to measure PL from RlBE GaN samples before and after photo-assisted wet etching in an 85% KOH:H20 (1:3) solution. The RIBE treatment decreased near band-edge PL intensity by a factor of approximately five, whereas subs...

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Planar geometry, lateral Schottky rectifiers were fabricated on high resistivity AlxGa1−xN (x=0–0.25) epitaxial layers grown on sapphire substrates. The reverse breakdown voltages of unpassivated devices increased with Al composition, varying from 2.3 kV for GaN to 4.3 kV for Al0.25Ga0.75N. The reverse current–voltage (I–V) characteristics showed classical Shockley–Read–Hall recombination as the dominant mechanism, with I∝V0.5. The reverse current density in all diodes was in the range 5–10×10−6 A cm−2 at 2 kV. The use of p+ guard rings was effective in preventing premature edge breakdown and with optimum ring width increased VB from 2.3 to 3.1 kV in GaN diodes.

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Surface oxidation as a diffusion barrier for Al deposited on ferromagnetic metalsElectron microscopy study of interfacial reaction between eutectic SnPb and Cu/Ni(V)/Al thin film metallizationThe insertion of chemically vapor deposited graphene layers between Al metallization and Si substrates and between Au and Ni metal layers on Si substrates is shown to provide a significant reduction in spiking and intermixing of the metal contacts and reaction with the Si, where the bilayer graphene was transferred to the samples after the Cu-foil was etched. The graphene prevents reaction between Al and Si up to the temperatures of 700 C and the intermixing of Au and Ni up to the temperatures of at least 600 C. The outstanding performance of the graphene as a metal diffusion barrier will be very useful to improve the stability of the metallizations at elevated temperatures.