14.2 Quantum Wires
403
(a)
(b)
Fig. 14.3 a Transmission electron microscopy cross-sectional image of a crescent-shaped single GaAs/AlGaAs quantum
wire. From [1342], reprinted with permission, ©1994 IOP. (b) TEM cross-sectional image of a vertical stack of identical
GaAs/AlGaAs crescent-shaped QWRs. From [1341], reprinted with permission, ©1992, Elsevier Ltd
Fig. 14.4 a Plan-view SE image of single QWR, showing top and sidewall with QWR in the center. The white dashed
line indicates the position of the linescan on which the CL spectra linescan b has been taken at T = 5 K. The CL intensity
is given on a logarithmic false color scale to display the full dynamic range as a function of wavelength and position.
Adapted from [1342], reprinted with permission, ©1994 IOP
visualizes a linear tapering of the sidewall QW from about 2.1 nm thickness at the edge to 3 nm in the
center. The QWR luminescence itself appears at about 800 nm.
After fast capture from the barrier into the QWs and, to a much smaller extent corresponding to
its smaller volume, into the QWR, excess carriers will diffuse into the QWR via the adjacent sidewall
QW and the vertical QW. The tapering of the sidewall QW induces an additional drift current.
14.2.2 Cleaved-Edge Overgrowth Quantum Wires
Another method to create quantum wires of high structural perfection is cleaved-edge overgrowth
(CEO) [1343], shown schematically in Fig. 14.5. First, a layered structure is grown (single or multiple
quantum wells or superlattice). Then, a {110} facet is fabricated by cleaving (in vacuum) and epitaxy
403
(a)
(b)
Fig. 14.3 a Transmission electron microscopy cross-sectional image of a crescent-shaped single GaAs/AlGaAs quantum
wire. From [1342], reprinted with permission, ©1994 IOP. (b) TEM cross-sectional image of a vertical stack of identical
GaAs/AlGaAs crescent-shaped QWRs. From [1341], reprinted with permission, ©1992, Elsevier Ltd
Fig. 14.4 a Plan-view SE image of single QWR, showing top and sidewall with QWR in the center. The white dashed
line indicates the position of the linescan on which the CL spectra linescan b has been taken at T = 5 K. The CL intensity
is given on a logarithmic false color scale to display the full dynamic range as a function of wavelength and position.
Adapted from [1342], reprinted with permission, ©1994 IOP
visualizes a linear tapering of the sidewall QW from about 2.1 nm thickness at the edge to 3 nm in the
center. The QWR luminescence itself appears at about 800 nm.
After fast capture from the barrier into the QWs and, to a much smaller extent corresponding to
its smaller volume, into the QWR, excess carriers will diffuse into the QWR via the adjacent sidewall
QW and the vertical QW. The tapering of the sidewall QW induces an additional drift current.
14.2.2 Cleaved-Edge Overgrowth Quantum Wires
Another method to create quantum wires of high structural perfection is cleaved-edge overgrowth
(CEO) [1343], shown schematically in Fig. 14.5. First, a layered structure is grown (single or multiple
quantum wells or superlattice). Then, a {110} facet is fabricated by cleaving (in vacuum) and epitaxy