Enhanced Photoluminescence from Long Wavelength InAs Quantum Dots Embedded in a Graded (In,Ga)As Quantum Well
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Enhanced Photoluminescence from Long Wavelength InAs Quantum Dots Embedded in a Graded (In,Ga)As Quantum Well L. Chen, V. G. Stoleru, D. Pal, D. Pan, and E. Towe Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904 ABSTRACT Three sets of self-organized InAs quantum dots (QDs) embedded in an external InGaAs quantum well samples were grown by solid source molecular beam epitaxy (MBE). By modifying Indium composition profile within quantum well (QW) region, it’s found the photoluminescence emission from quantum dots can be greatly enhanced when employing a graded quantum well to surround QDs. This quantum dots in a graded quantum well structure also preserves the long wavelength (1.3 µm) spectrum requirement for the future use in optoelectronics devices. INTRODUCTION The first GaAs-based quantum-dot laser was reported in 1994 [1]. Since then, remarkable progress has been made in the development of this device. Edge-emitting lasers operating from 1.0 to 1.3 µm with very low threshold currents have been reported [2,3,9]; in addition, verticalcavity surface-emitting lasers (VCSELs) have also been successfully demonstrated [4]. There are currently several approaches to grow 1.3 µm (In,Ga)As quantum dots by MBE. These include (i) the alternate supply of group-III and group-V source materials to form the (In,Ga)As dots [5], (ii) very slow growth (
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