Fabrication and characterization of epitaxial AlN/TiN bilayers on sapphire

We have grown high quality AlN/TiN heterostructures on sapphire (0001) substrates using the pulsed laser deposition (PLD) technique. The X-ray diffraction studies revealed that the AlN (0002) and TiN (111) planes were parallel to the sapphire (0006) plane and the rocking curve full widths at half maximum (FWHM) were 0.2°-0.3° for these layers. The AlN/TiN interface was found to be sharp from secondary ion mass spectrometry (SIMS) studies. The electrical resistivity of the epitaxial TiN buffer layer was as low as 14 μΩ, cm at room temperature, indicating that TiN could be an excellent contact material for nitride based wide bandgap semiconductor devices. The reflection spectrophotometry measurements showed that the AlN layer deposited on top of the TiN buffer retained its bulk optical properties having a refractive index of 2.25 and an energy gap larger than 5.9 eV. The electrical transport across the TiN/AlN/TiN capacitor could be explained with the ionic conduction model. © 1998 Elsevier Science S.A. All rights reserved.