Characterization of GaN/InGaN multiple quantum wells grown on sapphire substrates by nano-scale epitaxial lateral overgrowth technique
β Scribed by W.K. Fong; K.K. Leung; Charles Surya
- Book ID
- 104022069
- Publisher
- Elsevier Science
- Year
- 2011
- Tongue
- English
- Weight
- 455 KB
- Volume
- 318
- Category
- Article
- ISSN
- 0022-0248
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β¦ Synopsis
High-quality GaN/InGaN multiple quantum wells (MQWs) were fabricated on nano-scale epitaxial lateral overgrown (NELO) GaN layers. To grow the NELO layer first a 200 nm-thick SiO 2 was deposited on a 2 mmthick undoped GaN layer. A 10 nm-thick Ni layer was then deposited on the SiO 2 film followed by an annealing process to form nano-scale Ni clusters. These Ni clusters will serve as a dry etch mask for the underlying SiO 2 layer, resulting in the formation of SiO 2 islands of diameter and inter-distance of 300 and 200 nm, respectively. Undoped NELO GaN layer of thickness 2 mm was grown on the template with SiO 2 growth mask using metal organic chemical vapor deposition technique. A 2 mm-thick n-GaN epilayer and a 5-period GaN/InGaN MQWs were grown on top of the NELO layer. It is found that the overgrown GaN epilayers exhibit a significant reduction in threading dislocation (TD). From the atomic force microscopy characterizations, the TD density reduces from 3 Γ 10 8 to 6 Γ 10 7 cm Γ 2 by utilizing the NELO technique. Optical properties of the MQWs deposited on the NELO layer (type N) were characterized by temperature-dependent photoluminescence (PL). The results are compared to a control structure (type C) grown in the same growth run as the type N structures but without the NELO layer. It is found that type N sample exhibits three-fold improvement in PL intensity at room temperature. The increase in external quantum efficiency arises from both enhanced extraction efficiency and internal quantum efficiency. Detailed temperature-dependent PL studies were conducted to evaluate the relative improvement in internal quantum efficiency to account for the improved material quality when MQWs were grown on top of NELO epilayers.
π SIMILAR VOLUMES
InGaN/GaN multiple quantum-wells (MQWs) on Ga-polarity GaN by plasma-assisted molecularbeam epitaxy were grown and characterized. In-situ reflection high-energy-electron diffraction observations and high-resolution X-ray diffraction results indicated that a flat interface and a good periodicity of t