Packaging and interconnect technologies for the development of GaN nanowire-based light emitting diodes

Abstract

c-axis oriented GaN nanowires (NWs) grown on Si(111) using nitrogen plasma assisted molecular beam epitaxy (MBE) offer promising new approaches for realizing efficient LED technology. The nanowires grow remarkably free of defects, suggesting that eventual LED structures may operate with high quantum efficiencies. Furthermore, the dense NW morphology offers LED configurations with high light extraction efficiency compared to conventional planar LED structures. Interconnecting these vertically aligned nanowires is challenging because of their small diameters, extremely high aspect ratios, and random distributions on the substrate. We have developed novel packaging and interconnection methods by atomic layer deposition (ALD) multilayer encapsulation of the nanowires with 50 nm thick alumina layers and 40 nm thick tungsten layers. This nano-scaled multilayer also provides efficient thermal connections that are mechanically reliable. These encapsulated NWs were used as thermal test structures and the temperature dependence of the photoluminescence peak position as recorded from the portions of the nanowire protruding from the encapsulation was used to monitor the sample temperature. In principle, the internal junction-to-substrate thermal resistance of eventual NW LED structures could be reduced by 400 times by electroplating copper into the interstitial regions between the NWs. These novel packaging and interconnect technologies developed for GaN nanowire-based LEDs can be applied to many other nanowire-based microsystems.