M. E. Kordesch

IIIB-nitride semiconductors for high temperature electronic applications

Thin films of ScN and YN were grown on silicon, quartz and sapphire using metal evaporation and an RF atomic nitrogen source. YN decomposes on contact with water vapor, and only AlN capped films could be stabilized. ScN is stable in air and water, and thin films of this material deposited at temperatures between 300 and 900 C show a substrate-dependent film texture. Typical growth rates were {approximately} 0.1 nm/second with a 300 W N discharge at about 0.1 mTorr Nitrogen pressure. Structural characterization by x-ray diffraction, infrared transmission spectroscopy and Hall effect measurements on n-type ScN and the fabrication of p-n junctions of n- type ScN with silicon are presented.

Visible Emission from Thin-Film Phosphors of Amorphous AlN:Cu, Mn, and Cr

Luminescence studies of amorphous AlN doped with Cu, Mn, or Cr were performed at 300 K. Thin films of Cu, Mn, and Cr doped amorphous AlN, ∼200 nm thick, were grown on p-doped silicon (111) substrates using RF magnetron sputtering in a nitrogen atmosphere. Cathodoluminescence (CL) showed that pure Cu doped amorphous AlN has strong emission in the blue (∼420 nm) and Mn and Cr doped films luminesce in the red (∼690 nm). Cr +3 emission is more intense than Mn+4 because chromium does not suffer from incomplete charge compensation in the III-V semiconductor. Luminescence studies of crystalline and amorphous AlN:Mn thin films showed a red shift in the emission peak by almost 100 nm and is believed to be caused by the different crystal field of the amorphous host compared to the crystalline host material. Secondary ion mass spectrometry (SIMS) depth profiling was conducted to confirm the presence of the Cu and Cr in the films and to show the amount of dopant in relation to the Si substrate.

Amorphous Nitride Alloys as Hosts for Rare-Earth Luminescent Ions.

Amorphous alloys of aluminum-gallium nitride doped with erbium (Er) were deposited at 300 K. The compositions ranged from 19% Al to 86% Al with optical band gaps varying linearly with composition from 3.4 eV (GaN) to 6.2 eV (AlN). The films were deposited on p-doped silicon (111) by a dc/rf dual gun system in a nitrogen/argon atmosphere at a pressure of 4.8 milli-Torr. After growth the films were thermally “activated” at 1070 K for 10 minutes in a nitrogen atmosphere. The cathodoluminescence emission intensities decreased linearly with Ga composition. This dependence suggests that the higher energy transitions in the Er ion are quenched by transitions to the conduction band of the alloys.