Abstract
Abstract Impact of combinational (In0.21Al0.21Ga0.58As/In0.15Ga0.85As and In0.15Ga0.85As/ In0.21Al0.21Ga0.58As) capping on the strain, photoluminescence, and thermal stability of self-assembled InAs quantum dots (QDs) have been analyzed in this article. The proposed combinational capped QDs exhibited redshift in the ground state photoluminescence (PL) peak compared to the previously reported conventional capped QDs. The thickness of capping layers has also been varied to realize the optimum combination with minimized strain in the heterostructure. Room temperature emission at 1.33 µm along with a narrower full width at half maximum (FWHM) has been obtained for the 2.5/2.5 nm In0.21Al0.21Ga0.58As/In0.15Ga0.85As capped QD, which comes under the O-band of telecommunication wavelength. The probability of pulse broadening is less in this region, which might not only enhance the coupling of dots to the optical field but also increase the modal gain of QD based lasers, necessary for efficient long-haul telecommunication. Furthermore, the interface quality across the capping layers of the proposed QD heterostructure has been found to be smooth from transmission electron microscopy images. Thermal stability of the proposed QD structures, with optimum capping thickness, has been investigated through rapid thermal annealing (RTA) treatment. To ensure the reliability of the optimized structure for infrared applications, QD based photodetectors were fabricated and characterized. The lowest dark current and spectral response (up to 90 K) at the mid-infrared (MIR) regime was offered by the device having In0.21Al0.21Ga0.58As/In0.15Ga0.85As as the capping layer. A concise study of the improvement in opto-electronic properties of QDs via proposed combinational capping have been done in this article, which ultimately motivates towards the fabrication of photodetectors/ photoemitters and their integration on photonic chips.
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