Structural Characterization of Homoepitaxial Blue GaInN/GaN Light-Emitting Diodes by Transmission Electron Microscopy
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- Zhu, M., Xia, Y., Zhao, W. et al. Journal of Elec Materi (2008) 37: 641. doi:10.1007/s11664-008-0392-9
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We perform a transmission electron microscopy (TEM) characterization of blue light-emitting diode epiwafers grown homoepitaxially on a c-plane GaN substrate and compare with such grown on sapphire. We find a threading dislocation (TD) density as low as 2 × 108 cm−2 in homoepitaxial growth, which is 1/30 of that in sapphire-based material. A unique type of inverted pyramid defect with diameter ∼650 nm was observed. It originates from the homo-interface in edge-type TDs. TDs were also found to be generated within the quantum wells without a precursor TD defect. Otherwise, high-resolution TEM suggests extremely homogeneous quantum wells and barriers in terms of composition and well width. Besides plan-view TEM, wet chemical etching on n-type GaN was carried out in hot phosphoric acid to evaluate the TD density more quickly. The two methods prove to be equivalent with respect of determined TD densities.