InAs Quantum Dots Capped by GaAs, In0.4Ga0.6As Dots, and In0.2Ga0.8As Well
We have fabricated and characterized three types of InAs quantum dots (QDs) with different In
As capping layers. Post-growth atomic force microscopy measurements
show that the In0.2Ga0.8As/InAs structure has a smooth surface (dot-in-well structure), whereas the In0.4Ga0.6As/InAs structure revealed large QDs with a density
similar to that underneath InAs QDs on GaAs (dot-in-dot). With increasing In mole fraction of the capping layer and increasing In0.4Ga0.6As thickness, the energy position of the room-temperature
photoluminescence (PL) peak is red-shifted. The quantum dot-in-dot structure emits stronger room-temperature PL than does the quantum dotin-well structure. With a spatially distributed strain in the InAs
quantum dot, we have solved the three-dimensional Schrödinger equation by the Green's function theory for the eigenvalues and eigen wave functions. It is concluded that the ground state increases its
wave function penetration into the low-barrier In
As capping layer so that its energy position is red-shifted. The reduced PL peak intensity of the dot-in-well
(compared with GaAs covered dots) is due to the reduced overlapping between the ground state and the extended states above the GaAs barrier. The overlapping reduction in the dot-in-dot is over compensated
for by the reduced relaxation energy (full width at half-maximum), indicating the importance of the sample quality in determining the PL intensity.
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ENERGY BAND STRUCTURE;
INAS QUANTUM DOT;
LOCAL DENSITY OF STATES;
Document Type: Research Article
Physical Electronics and Photonics, Microtechnology Center at Chalmers, Department of Physics, Fysikgränd 3, Chalmers University of Technology and Gothenburg University,
Photonics Laboratory, Microtechnology Center at Chalmers, Department of Microelectronics ED, Chalmers University of Technology, Göteborg, Sweden
Publication date: 2002-07-01
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