Journal of Physical Chemistry & Biophysics
Open Access
ISSN: 2161-0398
+44 1478 350008
ISSN: 2161-0398
+44 1478 350008
K D Moiseev, V V Romanov, P A Dement�ev, V N Nevedomsky and E V Ivanov
Ioffe Institute, Russia
Posters-Accepted Abstracts: J Phys Chem Biophys
Nowadays there is a strong demand of heterostructures based on low-dimensional systems (quantum dots (QDs), quantum dashes (Q-dashes), nanowires etc.) for potential applications in optoelectronic devices for detection of various chemical, explosive and biological agents, which have pronounced absorption bands in the infrared wavelength range (2-5 �¼m). To penetrate in the long-wavelength region (�»>2 �¼m) it is necessary to produce nanoobjects inserted in matrices with the energy gap as narrow as 0.7 eV (for example, GaS band InAs). InSb/InAs quantum dot (dash) heterostructures are promising for the fabrication of the optoelectronic devices (light-emitting diodes and photodetectors) which can operate in the range of 3-5 �¼m.The arrays of InSb QDs and Q-dashes were obtained on InAs(001) substrate by combine technology based on liquid-phase epitaxy (LPE) and metalorganic vapour epitaxy (MOVPE) methods. Bimodal distribution in a size of the InSb nano-objects, low-density (5 �� 108 cm-2) large QDs with 12 nm in a height and high-density (1 �� 1010 cm-2) small QDs with a height of 3 nm, was observed for both growth technologies. Using of the InAsSbP matrix layers lattice-matched with InAs substrate resulted in the uniform distribution in a height of the InSb QDs due to a considerable change of a surface chemistry. The wetting layer thickness was dependent on matrix layer: 2 nm for the InAs surface and 1.3 nm for the InAsSbP one. LPE-grown coherent small QDs with convex lens-like shape were found to be dislocation-free without any extended defects according with Stranski- Krastanow mode. Transformation of a shape from a truncated pyramid formed by (111) planes and confined by (011) plane at the top to a multifaceted dome formed by (111) and (443) planes with octagon base and a flat top formed by (233) and (113) planes was discovered for the large QDs. A drastic change of the nanoobjects geometry from QD to Q-dash in dependence on MOVPE growth conditions was observed. The InSb Q-dashes with density of 2.5 �� 109 cm-2 were self-oriented by 500 nm length along [110] direction. These Q-dashes can be considered as intermediate step from QD arrays to horizontal nanowires. Heterostructures with the InSb QDs/Q-dashes buried into the InAs-based matrix exhibited intense electroluminescence (3.34 �¼m at 77 K and 3.62 �¼m at 300 K) under both forward and reversed bias. The blue shift of the EL peak from 3.34 to 3.22 �¼m with increasing of a drive current was observed at low temperatures. The obtained emission band can be ascribed to indirect radiative recombination transitions of electrons from self-adjacent quantum wells on the InAs side with holes localized on the Q-dash states. The interface-induced luminescence dominated for the nanoheterostructures and was comparable in intensity with interband EL in the n-InAs bulk (3.46 �¼m) at room temperature. For comparison, study of EL properties of the heterostructures with the InSbQDs inserted into the InAs matrix will be presented too. Evolution of the EL spectra and I-V characteristics behavior in dependence on applied external bias (forward and reverse) and heterostructure construction will be considered. Energy band diagram of the type II broken-gap InSb/InAs heterostructure with localized states will be proposed and discussed.
Email: mkd@iropt2.ioffe.ru