In this study, GaN m‐plane Schottky barrier diodes fabricated with a metalorganic vapor‐phase epitaxy on a GaN substrate were investigated using emission microscope, photoluminescence, and cathodoluminescence. In addition, facet dependence of leakage current under reverse‐biased condition was observed. We showed that the leakage‐current distribution was caused by the facet dependence of the carrier concentration and oxygen concentration. These results can provide important suggestions for the fabrication of m‐plane devices. (a) four‐faceted hillocks on m‐plane GaN MOVPE sample, facet dependence of (b) leakage current and (c) PL peak intensity of the m‐plane GaN Schottky barrier diode.

In this study, GaN m‐plane Schottky barrier diodes are fabricated by metalorganic vapor‐phase epitaxy (MOVPE) on several off‐angle gallium nitride (GaN) substrates, and the off‐cut angle dependence of impurity incorporation is investigated. We show that the MOVPE layer on the substrate inclined 5° toward the [000–1] direction has extremely low impurity incorporation. These results provide important suggestions for the fabrication of m‐plane power devices.

No abstract

GaN vertical Schottky barrier diodes (SBDs) were grown on m-plane GaN substrates by metalorganic vapor phase epitaxy (MOVPE) using a quartz-free flow channel (FC). The use of the quartz-free FC reduced the impurity concentrations of silicon and carbon by factors of 2 and 10, respectively, compared with the concentrations obtained using a conventional reactor with a quartz FC. The oxygen concentration was found to decrease with increasing the layer thickness. We achieved the same impurity concentration for the epitaxial layers grown on m-plane GaN substrates as for those grown on c-plane GaN substrates under the same growth conditions. A high resistivity of unintentionally doped GaN was achieved by decreasing the impurity concentration. Additionally, for the further understanding of the low impurity concentration in the m-plane GaN, the n-type GaN was inserted between the m-plane GaN substrate and the drift layer. The results revealed that the c- and m-plane breakdown voltages and leakage currents have similar tendencies.

The reduction of unintentional impurities in m-plane 10 10Þð GaN homoepitaxial layers is demonstrated by using nitrogen (N 2 ), as opposed to hydrogen (H 2 ), as carrier gas in metalorganic vapor phase epitaxy (MOVPE). Secondary ion mass spectrometry (SIMS) analysis shows that the impurity levels of residual oxygen (O), carbon (C), and silicon (Si) are decreased by nearly one order of magnitude in N 2 -grown samples. Although the full width at half maximum (FWHM) values for the on-axis m-plane X-ray rocking curves of all specimens are quite similar (around 50 arcsec), plan-view scanning transmission electron microscopy (STEM) measurements reveal a clear reduction of dislocation densities in N 2 -grown films. Their origin is likely related to an initial surface roughening with H 2 carrier gas, which also causes surface faceting resulting in the formation of large four-sided pyramidal hillocks, while using N 2 results in smoother surfaces. Hence, MOVPE growth with N 2 carrier gas is an effective method to lower the impurity incorporation in mplane GaN materials in addition to reducing the formation of defects and improving the surface morphology, which can enable the development of high-performance GaN-based devices on non-polar surfaces.GaN is an attractive material for optoelectronics and high-power electronics applications, due to its direct wide band gap, high electron mobility, high electron saturation velocity, high stability and conductivity. GaN materials grown in non-polar orientations (a-or m-plane) are devoid of spontaneous polarization and piezoelectric fields which can enable novel highperformance electronic devices owing to the suppression of the quantum confined Stark effect. [1] As a result, extensive and ongoing research efforts have been devoted to the growth and characterization of nonpolar nitrides worldwide in order to better comprehend their material properties and challenges. Moreover, the advent of low defect lattice-matched bulk GaN substrates has provided a significant progress for high-quality GaN crystals, and improved performance of GaN-based devices. [2] Hitherto, promising results have been reported for light-emitting diodes, [3] laser diodes, [4] and normally off high-electron-mobility transistors [5] on nearly dislocation-free m-plane GaN (m-GaN) substrates. However, homoepitaxial m-GaN films grown on nominally on-axis bulk GaN by metalorganic vapor phase epitaxy (MOVPE) commonly exhibit wavy surface morphologies featuring pyramidal hillocks and are prone to high impurity intake. [6][7][8] While the surface morphology can be improved by using much expensive miscut GaN substrates, [6] the higher unintentional oxygen (O), carbon (C), and silicon (Si) impurities incorporation in m-plane GaN layers remains an issue which hinders further progress in device performance and reliability. Therefore, it is crucial to enhance the material properties of homoepitaxial m-plane GaN in the most cost-effective way via epitaxial growth engineering.Early works on the MOVPE growth of III-V materials es...