• Lee, Hsuan-Ping
• Bayram, Can
• Liu, R.
• Schaller, Richard

Abstract

<jats:title>Abstract</jats:title><jats:p>Here we study and correlate structural, electrical, and optical properties of three GaN samples: GaN grown by metalorganic chemical vapor deposition on sapphire (GaN/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>), freestanding GaN crystals grown by the high nitrogen pressure solution method (HNPS GaN), and GaN grown by hydride vapor phase epitaxy on silicon (GaN/Si). Defect and impurity densities and carrier concentrations are quantified by x-ray diffraction, secondary mass ion spectroscopy, and Hall effect studies, respectively. Power-dependent photoluminescence measurements reveal GaN near-band-edge emissions from all samples having mixtures of free exciton and band-to-band transitions. Only the defect luminescence in the GaN/Si sample remains unsaturated, in contrast to those from the HNPS GaN and GaN/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> samples. Carrier lifetimes, extracted from time-resolved photoluminescence measurements, and internal quantum efficiencies, extracted from temperature-dependent photoluminescence measurements, are used to extract radiative and nonradiative lifetimes. Shockley–Read–Hall (A) and radiative recombination coefficients (B) are then calculated accordingly. Overall, the A coefficient is observed to be highly sensitive to the point defect density rather than dislocation density, as evidenced by three orders of magnitude reduction in threading dislocation density reducing the A coefficient by one order of magnitude only. The B coefficient, while comparable in the higher quality and lowly doped GaN/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> and HNPS GaN samples, was severely degraded in the GaN/Si sample due to high threading dislocation density and doping concentration.</jats:p>

Topics

• density
• impedance spectroscopy
• photoluminescence
• phase
• x-ray diffraction
• Nitrogen
• dislocation
• Silicon
• chemical vapor deposition
• point defect
• ion spectroscopy