Internal quantum efficiency of III-nitride quantum dot superlattices grown by plasma-assisted molecular-beam epitaxy

Journal Article · Sun May 15 00:00:00 EDT 2011 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3590151· OSTI ID:21560258

Gacevic, Z ^[1]; Das, A; Kotsar, Y; Kandaswamy, P K; Monroy, E ^[1]; Teubert, J ^[1]; Kehagias, Th; Koukoula, T; Komninou, Ph ^[2]

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1. CEA-CNRS Group 'Nanophysique et Semiconducteurs', CEA-Grenoble, INAC/SP2M 17 rue des Martyrs, 38054 Grenoble (France)
2. Physics Department, Aristotle University of Thessaloniki, GR 54124 Thessaloniki (Greece)

We present a study of the optical properties of GaN/AlN and InGaN/GaN quantum dot (QD) superlattices grown via plasma-assisted molecular-beam epitaxy, as compared to their quantum well (QW) counterparts. The three-dimensional/two-dimensional nature of the structures has been verified using atomic force microscopy and transmission electron microscopy. The QD superlattices present higher internal quantum efficiency as compared to the respective QWs as a result of the three-dimensional carrier localization in the islands. In the QW samples, photoluminescence (PL) measurements point out a certain degree of carrier localization due to structural defects or thickness fluctuations, which is more pronounced in InGaN/GaN QWs due to alloy inhomogeneity. In the case of the QD stacks, carrier localization on potential fluctuations with a spatial extension smaller than the QD size is observed only for the InGaN QD-sample with the highest In content (peak emission around 2.76 eV). These results confirm the efficiency of the QD three-dimensional confinement in circumventing the potential fluctuations related to structural defects or alloy inhomogeneity. PL excitation measurements demonstrate efficient carrier transfer from the wetting layer to the QDs in the GaN/AlN system, even for low QD densities ({approx}10{sup 10} cm{sup -3}). In the case of InGaN/GaN QDs, transport losses in the GaN barriers cannot be discarded, but an upper limit to these losses of 15% is deduced from PL measurements as a function of the excitation wavelength.

• OSTI ID: 21560258
• Journal Information: Journal of Applied Physics, Vol. 109, Issue 10; Other Information: DOI: 10.1063/1.3590151; (c) 2011 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM NITRIDES
ATOMIC FORCE MICROSCOPY
CRYSTAL DEFECTS
DENSITY
EXCITATION
FLUCTUATIONS
GALLIUM NITRIDES
INDIUM COMPOUNDS
LAYERS
MOLECULAR BEAM EPITAXY
MOLECULAR STRUCTURE
PHOTOLUMINESCENCE
QUANTUM DOTS
QUANTUM EFFICIENCY
QUANTUM WELLS
SEMICONDUCTOR MATERIALS
STACKING FAULTS
SUPERLATTICES
TRANSMISSION ELECTRON MICROSCOPY
ALUMINIUM COMPOUNDS
CRYSTAL GROWTH METHODS
CRYSTAL STRUCTURE
EFFICIENCY
ELECTRON MICROSCOPY
EMISSION
ENERGY-LEVEL TRANSITIONS
EPITAXY
GALLIUM COMPOUNDS
LUMINESCENCE
MATERIALS
MICROSCOPY
NANOSTRUCTURES
NITRIDES
NITROGEN COMPOUNDS
PHOTON EMISSION
PHYSICAL PROPERTIES
PNICTIDES
VARIATIONS