Characterization of Bulk GaN Crystals Grown From Solution at Near Atmospheric Pressure

摘要

The properties of GaN crystals grown from solution at temperatures ranging from 780 to 810 1C and near atmospheric pressure 0.14 MPa, have been investigated using low temperature X-band (9.5 GHz) electron paramagnetic resonance spectroscopy, micro-Raman spectroscopy, photoluminescense spectroscopy, and photoluminescence imaging. Our samples are spontaneously nucleated thin platelets of approximate dimensions of 220.025 mm3, or samples grown on both polycrystalline and single crystal HVPE large-area (380.5 mm3) seeds. Electron paramagnetic resonance spectra consists of a single Lorentzian line with axial symmetry about the c-axis, with approximate g-values, gJ 1.951 and gJ 1.948 and a peak-to-peak linewidth of 4.0 G. This resonance has been previously assigned to shallow impurity donors/conduction electrons in GaN and attributed to Si- and/or O impurities. Room temperature photoluminescence and photoluminescence imaging data from both Ga and N-faces show different dominant emission bands, suggesting different incorporation of impurities and/or native defects. Raman scattering and X-ray diffraction show moderate to good crystalline quality.