Improved quality non-polar III-nitride heteroepitaxial films and devices

GaN and its compounds suffer from polarization fields when grown along the c-⟨0001⟩ direction. These polarization fields result in poor carrier recombination efficiencies in quantum wells and shift in emission wavelength caused by the quantum confined stark effect due to spatial separation of the electron and hole wavefunction separation. It is possible to eliminate these effects by growing along one of the nonpolar directions, namely a-⟨11 20⟩ or m-⟨1100⟩, so that the polarization fields are normal to the growth direction. However films grown along these nonpolar directions suffer from high defect densities. Consequently, devices structures grown with these orientations suffer from poor electrical and optical characteristics.; In this dissertation these two issues were addressed so as to eliminate the polarization fields by nonpolar growth along the m-⟨11 00⟩ direction with metalorganic chemical vapor deposition (MOCVD) and to effectively reduce the high defect densities in films grown along the nonpolar directions employing a new growth technique, sidewall lateral epitaxial overgrowth (SLEO).; Previously, device-quality nonpolar a-⟨1120⟩ plane GaN films were achieved. Growth along this plane however was extremely sensitive to changes in growth conditions and was limited to low pressures and restricted precursor flows. In this dissertation it was shown that nonpolar m-⟨1100⟩ plane GaN films are more stable and less sensitive to changes in growth conditions. The first device-quality m-⟨1 100⟩ GaN films were then grown on m-plane 6H-SiC substrates with an AlN nucleation layer by MOCVD.; A new technique, SLEO, was developed to effectively reduce defect densities in nonpolar films. Using this method it is possible to reduce threading dislocation (TD) densities by 3-4 orders of magnitude to ∼106-10 7 cm-2 and stacking fault (SF) densities by 1-2 orders to ∼103-104 cm-1. This would improve the performance of devices subsequently grown on these high quality templates. For direct comparison, GaN/Al0.15GaN 360 nm UV LEDs were grown on co-loaded planar a-GaN, planar c-GaN and SLEO a-GaN templates. Devices grown on nonpolar SLEO films demonstrated ∼2-3x higher electron mobility, ∼3x lower series resistance, and ∼100-300x higher EQE when compared with the planar nonpolar films.