Applied Physics Letters · 1993 · 330 citations · 13 references
EngineeringElectrical EngineeringMaterials ScienceElectronic MaterialsSemiconductor DevicesSemiconductor MaterialsDopingMetal-semiconductor ContactsSemiconductor InterfacesSemiconductor PhysicsSemiconductor SurfacesWide-bandgap Semiconductor DevicesCurrent-voltage CharacterizationCurrent-voltage RelationsCurrent-voltage RelationshipGallium NitrideMolecular Beam EpitaxyOhmic MaterialsResistivityWork Function
We report measurements on the nature of aluminum and gold contacts to GaN. The GaN films were deposited onto the R-plane of sapphire substrates by molecular beam epitaxy and are autodoped n-type. Metal contacts were deposited by evaporation and were patterned photolithographically. Current-voltage characterization shows that the as-deposited aluminum contacts are ohmic while the as-deposited gold contacts are rectifying. The gold contacts become ohmic after annealing at 575 °C, a result attributed to gold diffusion. The specific contact resistivity of the ohmic aluminum and gold contacts were found by transfer length measurements to be of device quality (10−7–10−8 Ω m2). The results of these studies suggest a direct correlation between barrier height and work function of the metal, consistent with the strong ionic character of GaN.
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