Growth and Properties of III-V Nitride Films, Quantum Well Structures and Integrated Heterostructure Devices

Abstract

Growth of lll-V nitrides by molecular beam epitaxy (MBE) is being studied at NCSU using an rf nitrogen plasma source. GaN/SiC substrates consisting of ∼3 μm thick GaN buffer layers grown on 6H-SiC wafers by MOVPE at Cree Research, Inc. are being used as substrates in the MBE film growth experiments. The MBE-grown GaN films exhibit excellent structural and optical properties — comparable to the best GaN films grown by MOVPE—as determined from photoluminescence, x-ray diffraction, and vertical-cross-section TEM micrographs. Mg and Si have been used as dopants for p-type and n-type layers, respectively. Al_xGa_1−xN films (x∼0.06-0.08) and Al_xGa_1−xN/GaN multi-quantum-well structures have been grown which display good optical properties. Light-emitting diodes (LEDs) based on double-heterostructures of Al_xGa_1−xN/GaN which emit violet light at ∼400 nm have also been demonstrated. Key issues that must be addressed before lll-V nitride laser diodes can be demonstrated and commercialized are discussed. New integrated heterostructures are proposed for the development of a variety of vertical-transport devices such as light-emitting diodes, laser diodes, photocathodes, electron emitters based on the negative-electron-affinity of AIN, and certain transistor structures.