Strain compensation technique in self-assembled InAs/GaAs quantum dots for applications to photonic devices

• Published in: Journal of physics. D, Applied physics Vol. 42; no. 7; pp. 073002 - 073002 (12); [np]
• Main Authors: Tatebayashi, J, Nuntawong, N, Wong, P S, Xin, Y-C, Lester, L F, Huffaker, D L
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 07.04.2009; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Nanoscale materials and structures: fabrication and characterization; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Quantum dots; Defect density; Gallium arsenides; Stacking sequence; Quantum dots; Photoluminescence; Self-assembled layers; XRD; MOCVD; Indium arsenides; Thickness; Energy gap; Strained layer; Strain distribution
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/42/7/073002

We report the strain compensation (SC) technique for a stacked InAs/GaAs self-assembled quantum dot (QD) structure grown by metalorganic chemical vapour deposition (MOCVD). Several techniques are used to investigate the effect of the SC technique: the high-resolution x-ray diffraction (XRD) technique is used to quantify the reduction in overall strain, atomic force spectroscopy is used to reveal that the SC layer improves the QD uniformity and reduces the defect density and photoluminescence characterization is used to quantify the optical property of stacked InAs QDs. In addition, experimental and mathematical evaluation of reduction in the strain field in the compensated structure is conducted. We identify two types of strain in stacked QD samples, homogeneous and inhomogeneous strain. XRD spectra indicate that vi > 36% reduction in the homogeneous strain can be accomplished. Inhomogeneous strain field is investigated by studying the strain coupling probability as a function of the spacer thickness, indicating that 19% reduction in inhomogeneous strain within SC structures has been evaluated. Next, device application of SC techniques including lasers and modulators is reported. Room temperature ground-state lasing from 6-stack InAs QDs with GaP SC is realized at a lasing wavelength of 1265 nm with a threshold current density of 108 A cm-2. The electro-optic (EO) properties of 1.3 mum self-assembled InAs/GaAs QDs are investigated. The linear and quadratic EO coefficients are 2.4 X 10-11 m V-1 and 3.2 X 10-18 m2 V-2, respectively, which are significantly larger than those of GaAs bulk materials. Also, the linear EO coefficient is almost comparable to that of lithium niobate.