ICMCTF2003 Session PL: Plenary

Monday, April 28, 2003 8:30 AM in Room Town & Country

Monday Morning

Start	Invited?	Item
8:30 AM		PL-1 Chemical Vapor Process Routes and the Resulting Microstructural and Physical Characteristics of III-Nitride Films and Device Structures Robert F. Davis (North Carolina State University) The Group III-Nitrides of AlN, GaN and InN and their alloys have become key materials in the development and commercial realization of short-wavelength photonic devices for display, sources of white light, UV detectors and data storage. Considerable research has also been devoted to the development of high-frequency devices, specifically high-electron mobility transistors due to the induced polarization in the wurtzite structures and that due to the piezoelectric fields generated at the AlGaNGaN interface. These phenomena produce a two-dimensional electron gas having sheet electron densities as high as 5E13 cm-2 that leads to polarization-induced doping of the GaN. Essentially all III-Nitride films are heteroepitaxially grown on sapphire (Al2O3(0001)) or an SiC(0001) polytype via either metalorganic or hydride vapor phase epitaxy. The mismatches in lattice parameters and the coefficients of thermal expansion between the substrates and the deposited films significantly hamper the epitaxial growth of these films and device structures. As such, it is common to employ a buffer layer of GaN, AlN or donor (Si)-doped AlGaN between the substrate and the film. All the buffer layers and the GaN films deposited on AlN or AlGaN nucleate and grow as three dimensional flat islands which coalesce and produce threading dislocations that emanate from the resulting grain boundaries and that compromise the electrical and optical characteristics of the devices. Development of lateral epitaxial overgrowth and pendeo-epitaxy growth techniques have significantly reduced the density of threading dislocations in GaN and AlGaN layers, allowed commercialization of GaN-based laser diode and significantly improved the properties of microelectronic devices. The presentation will detail the various aspects of the primary process routes used to grow III-Nitride films and heterostructures and the methods employed to reduce the density of dislocations, describe the state of the art in bulk crystal growth and discuss the potential for future applications in white lighting and sensors.The Group III-Nitrides of AlN, GaN and InN and their alloys have become key materials in the development and commercial realization of short-wavelength photonic devices for display, sources of white light, UV detectors and data storage. Considerable research has also been devoted to the development of high-frequency devices, specifically high-electron mobility transistors due to the induced polarization in the wurtzite structures and that due to the piezoelectric fields generated at the AlGaNGaN interface. These phenomena produce a two-dimensional electron gas having sheet electron densities as high as 5E13 cm-2 that leads to polarization-induced doping of the GaN. Essentially all III-Nitride films are heteroepitaxially grown on sapphire (Al2O3(0001)) or an SiC(0001) polytype via either metalorganic or hydride vapor phase epitaxy. The mismatches in lattice parameters and the coefficients of thermal expansion between the substrates and the deposited films significantly hamper the epitaxial growth of these films and device structures. As such, it is common to employ a buffer layer of GaN, AlN or donor (Si)-doped AlGaN between the substrate and the film. All the buffer layers and the GaN films deposited on AlN or AlGaN nucleate and grow as three dimensional flat islands which coalesce and produce threading dislocations that emanate from the resulting grain boundaries and that compromise the electrical and optical characteristics of the devices. Development of lateral epitaxial overgrowth and pendeo-epitaxy growth techniques have significantly reduced the density of threading dislocations in GaN and AlGaN layers, allowed commercialization of GaN-based laser diode and significantly improved the properties of microelectronic devices. The presentation will detail the various aspects of the primary process routes used to grow III-Nitride films and heterostructures and the methods employed to reduce the density of dislocations, describe the state of the art in bulk crystal growth and discuss the potential for future applications in white lighting and sensors.