Effects of Rapid Thermal Annealing on the Intersubband Energy Spacing of Self-Assembled InAs/Gaas Quantum Dots
- PDF / 403,833 Bytes
- 7 Pages / 420.48 x 639 pts Page_size
- 58 Downloads / 183 Views
1, Centre for Optoelectronics, Department of Electrical Engineering, National University of Singapore, Singapore 119260, Singapore 2, Institute of Materials Research and Engineering, National University of Singapore, Singapore 119260, Singapore * Email address: [email protected] ABSTRACT In this paper, we showed the significant reduction of the energy spacing between ground state and excited state emissions from InAs/GaAs quantum dots due to interface interdiffusion induced by thermal treatment. In addition, the strong narrowing of the luminescence linewidth of the ground state and excited state emissions from the InAs dot layers for the annealed samples indicates an improvement of the sizedistribution of the QDs. Large blue-shift of the energy positions of both emissions was also observed. High resolution X-Ray diffraction experiments give strong evidence of the interface atom interdiffusion in the annealed samples. This work shows ability to tune the wavelength for applications like infrared detectors and lasers based on intrasubband transitions of self-assembled QDs. INTRODUCTION Self-assembled quantum dots (QDs) directly obtained via the so-called Stranski-Krastanow (SK) growth mode are of great interest due to their fundamental physics and potential device applications. Among them, InAs/GaAs QD is a representative system, which has been extensively investigated both experimentally [16] and theoretically. [6-10] However, the electronic structure of InAs dots still remains
an open problem. Indeed, the shape and size of the QDs as well as the strain distribution in and around them, which strongly affect the electronic structure, are very difficult to be accurately determined. Currently, most studies show that there are several bound levels rather than one bound state in the conduction band of InAs dots. Recently, intersubband transitions within the conduction band of the QDs have been demonstrated with different techniques,[l 1-16] and the quantum dot infrared
photodetectors based on such transitions have been reported. [ 17-191 Although the defect-free dots can be formed in lattice mismatched heterostructures by the SK growth mode, inevitable size distribution in the dots results in inhomogeneous broadening both for the photoluminescence (PL) emission from the interband transitions and infrared absorption due to the intersubband transitions in the dots. Therefore, further developments in the use of QD structures for devices such as lasers and detectors depend on the achievement of tunability of dot shape and sizes in
order to both control the wavelength and reduce the linewidth of the luminescence. Recently, powerful capability of post-growth thermal annealing in adjusting the shape and size and thus optical properties of self-assembled QDs has been shown by Leon et
al.,[20] Malik et al.[21] and us.[22] The main achievements of above work are the significant blue-shift and narrowing of PL peak due to interband transition between
electron and hole ground states of the dots. Large blue-shift of the PL peak is
Data Loading...
