Characterization of GaN/InGaN multiple quantum wells grown on sapphire substrates by nano-scale epitaxial lateral overgrowth technique

W. K. Fong, K. K. Leung, Charles Surya

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

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 SiO2 was deposited on a 2 μm-thick undoped GaN layer. A 10 nm-thick Ni layer was then deposited on the SiO2 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 SiO2 layer, resulting in the formation of SiO2 islands of diameter and inter-distance of 300 and 200 nm, respectively. Undoped NELO GaN layer of thickness 2 μm was grown on the template with SiO2 growth mask using metal organic chemical vapor deposition technique. A 2 μm-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 3×108 to 6×107 cm-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.

Original languageEnglish
Pages (from-to)488-491
Number of pages4
JournalJournal of Crystal Growth
Volume318
Issue number1
DOIs
Publication statusPublished - Mar 1 2011
Externally publishedYes

Keywords

  • A1. Multiple quantum wells
  • A1. Optical properties
  • A3. Epitaxial lateral overgrowth
  • B1. GaN

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Chemistry
  • Inorganic Chemistry

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