TiN/GaN Metal/Semiconductor Multilayer Nanocomposites Grown by Reactive Pulsed Laser Deposition

TiN/GaN multilayers with periods ranging from 5 nm to 50 nm were grown by reactive pulsed laser deposition (PLD) using elemental metal targets in an ammonia ambient at 20mtorr onto Si(100), MgO(100) and sapphire(0001) substrates. For growth on Si and MgO substrates, an epitaxial 40 nm thick TiN buffer layer was deposited prior to deposition of the multilayers. An epitaxial 150 nm GaN buffer layer was grown on sapphire substrates. For all substrates, layer thicknesses and periods investigated, x-ray diffraction and cross-sectional transmission electron microscopy revealed {0001} texture for GaN, and {111} texture for TiN in the multilayers. Both TiN layers and GaN layers thicker than ∼ 2nm appear to be continuous, with no evidence of agglomeration. Both phases are crystalline, with lateral grain sizes comparable to the layer thickness. These results suggest that epitaxy will not be necessary to fabricate pinhole free metal/semiconductor multilayers in the nitride system.