Long-wavelength room-temperature luminescence from InAs/GaAs quantum dots with an optimized GaAsSbN capping layer
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NANO EXPRESS
Open Access
Long-wavelength room-temperature luminescence from InAs/GaAs quantum dots with an optimized GaAsSbN capping layer Antonio D Utrilla, Jose M Ulloa*, Alvaro Guzman and Adrian Hierro
Abstract An extensive study on molecular beam epitaxy growth conditions of quaternary GaAsSbN as a capping layer (CL) for InAs/GaAs quantum dots (QD) was carried out. In particular, CL thickness, growth temperature, and growth rate were optimized. Problems related to the simultaneous presence of Sb and N, responsible for a significant degradation of photoluminescence (PL), are thereby solved allowing the achievement of room-temperature (RT) emission. A particularly strong improvement on the PL is obtained when the growth rate of the CL is increased. This is likely due to an improvement in the structural quality of the quaternary alloy that resulted from reduced strain and composition inhomogeneities. Nevertheless, a significant reduction of Sb and N incorporation was found when the growth rate was increased. Indeed, the incorporation of N is intrinsically limited to a maximum value of approximately 1.6% when the growth rate is at 2.0 ML s−1. Therefore, achieving RT emission and extending it somewhat beyond 1.3 μm were possible by means of a compromise among the growth conditions. This opens the possibility of exploiting the versatility on band structure engineering offered by this QD-CL structure in devices working at RT. Keywords: InAs; Quantum dots; GaAsSbN; Capping layer; Growth rate; Luminescence PACS: 81.15.Hi (molecular beam epitaxy); 78.55.Cr (III-V semiconductors); 73.21.La (quantum dots)
Background Tailoring the band structure and optical properties of the technologically mastered InAs/GaAs quantum dots (QDs) has been the focus of many efforts in the last decade. The use of a GaAsSb strain-reducing capping layer (CL) has been widely studied for that purpose [1-4]. The presence of Sb raises the valence band (VB) of GaAs [5] allowing the extending of QD emission over a wide wavelength range. Moreover, Sb suppresses the decomposition of GaAs-capped QDs [6] and has been shown to provide devices with improved characteristics [7-10]. Within this approach, the rise of the VB induced by the presence of Sb makes the band alignment structure become type II for contents of Sb above structures 14% to 16% [2-4]. A further step forward which has been recently proposed is the addition of N to the ternary * Correspondence: [email protected] Institute for Systems based on Optoelectronics and Microtechnology (ISOM) and Departamento de Ingeniería Electrónica, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, Madrid 28040, Spain
GaAsSb CL. The incorporation of N in GaAs, according to the band anticrossing model [11], reduces only the conduction band (CB) of GaAs the same way Sb raises only its VB. Therefore, the use of the quaternary GaAsSbN CL on InAs/GaAs QDs allows tuning independently the electron and hole confinement potentials, as it has already been demonstrated [12]. Moreover, this approach allows m
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