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-r ay diffraction studies revealed that the AlN (0002) and TiN (111) plan es were parallel to the sapphire (0006) plane and the rocking curve fu ll widths at half maximum (FWHM) were 0.2 degrees-0.3 degrees for thes e layers. The AlN/TiN interface was found to be sharp from secondary i on mass spectrometry (SIMS) studies. The electrical resistivity of the epitaxial TiN buffer layer was as low as 14 mu Omega cm at room tempe rature, indicating that TiN could be an excellent contact material for nitride based wide bandgap semiconductor devices. The reflection spec trophotometry measurements showed that the ALN layer deposited on top of the TiN buffer retained its bulk optical properties having a refrac tive index of 2.25 and an energy gap larger than 5.9 eV. The electrica l transport across the TiN/AlN/TiN capacitor could be explained with t he ionic conduction model. (C) 1998 Elsevier Science S.A. All rights r eserved.