Intense Monochromatic Light Emission from Multiple Nanoscale Twin Boundaries in Indirect-gap AlGaAs Epilayers

Abstract

The optical properties of multiple nanoscale twin boundaries in indirect-gap AlGaAs epilayers were studied. Twin boundaries of AE3-type, extended on {111}B, were self-organized in an epilayer during the epitaxial growth on an AlGaAs(001) substrate by metal-organic vapor-phase epitaxy. Polarized cathodoluminescence spectroscopy in a transmission electron microscope revealed that a set of parallel twin boundaries arranged at similar intervals of nanometer length emits an intense monochromatic light polarized parallel to the boundaries. The photon energy was tunable by controlling the intervals of the boundaries, without changing the crystal structure and the composition.

Formation of multiple nanoscale twin boundaries that emit intense light in indirect-gap AlGaAs epilayers

“…3), self-organized simultaneous with the S3-type boundaries, did not emit the 1.80-1.95 eV light. The results indicate that the origin of the 1.80-1.95 eV light is the S3-type boundaries, as we have proposed [8,9]. …”

“…Recently, it is demonstrated [8,9] that; parallel nanoscale twin boundaries in an indirect-gap AlGaAs epilayer, formed spontaneously by MOVPE, emit intense monochromatic light polarized parallel to the boundaries, and the photon energy is tunable by controlling the intervals of the boundaries without changing the crystal structure and the composition, as expected theoretically in twinning superlattices [3,4]. Such a possibility for band-structure engineering could be enhanced when combining with the variation of material compositions and doping patterns, especially for the GaAs-and silicon-based devices that have been fabricated with the well-established technology, if the means of fabricating twinning nanostructures are devised.…”

In-Situ Analysis of Optoelectronic Properties of Semiconductor Nanostructures and Defects in Transmission Electron Microscopes

“…(h). (Ohno et al, 2007b) CL mapping measurements reveal that (Ohno et al, 2007b), a CL light is emitted from a twinned layer, and the intensity is stronger in comparison with the band-to-band emission in direct-gap Al 0.2 Ga 0.8 As (Figs. 10b-10c), even though the layer is an indirect gap semiconductor.…”

“…Also, the techniques have been used to assess the carrier dynamics such as excited carrier paths towards the lower energy states (e.g., Akiba et al, 2004, Merano et al, 2005, Sonderegger et al, 2006, as well as carrier lifetimes. Some extended defects such as dislocations (Yamamoto et al, 1984, Mitsui & Yamamoto, 1997, twins (Ohno et al, 2007b), platelets (Ohno, 2005a) and strains induced by a uniaxial stress , Ohno, 2005b, as well as low-dimensional nanostructures such as nanowires (Ishikawa et al, 2008, Yamamoto et al, 2006, quantum wells (Ohno, 2005a) and superlattices (Ohno & Takeda, 2002, Ohno et al, 2007b, form anisotropic defect levels, and electronic transitions via the levels result in the emission of polarized CL lights. CL polarization analyses have helped us to assess quantitatively the atomistic structures of such nanostructures and defects.…”

“…Such quantum nanostructures have potentials for enhancing the device performance, and also their electron confinement produces quantum electronic states which provide an important system for fundamental physics. Recently, superlattices based on periodic changes of crystal directions, i.e., twinning superlattices (Ikonic et al, 1993), have been proposed in III-V (Xiong & Eklund, 2006, Ohno et al, 2007b, Algra et al, 2008, Bao et al, 2008, II-VI (Ikonic et al, 1996), and VI (Hibino et al, 1998, Fissel et al, 2006 semiconductors and in metals (e.g., Kobayashi & Uchihashi, 2010). It is expected that they can offer as much versatility in tailoring the miniband structure as there exists in heterostructure-based superlattices (e.g., Ikonic et al, 1993, Nakamura & Natori, 2006.…”