Effects of Dislocation\nFiltering Layers on Optical\nProperties of Third Telecom Window Emitting InAs/InGaAlAs Quantum\nDots Grown on Silicon Substrates

Integrating light emitters based on III–V materials\nwith\nsilicon-based electronics is crucial for further increase in data\ntransfer rates in communication systems since the indirect bandgap\nof silicon prevents its direct use as a light source. We investigate\nhere InAs/InGaAlAs quantum dot (QD) structures grown directly on 5°\noff-cut Si substrate and emitting light at 1.5 μm, compatible\nwith established telecom platform. Using different dislocation defect\nfiltering layers, exploiting strained superlattices, and supplementary\nQD layers, we mitigate the effects of lattice constant and thermal\nexpansion mismatches between III–V materials and Si during\ngrowth. Complementary optical spectroscopy techniques, i.e. photoreflectance\nand temperature-, time- and polarization-resolved photoluminescence,\nallow us to determine the optical quality and application potential\nof the obtained structures by comparing them to a reference sample–state-of-the-art\nQDs grown on InP. Experimental findings are supported by calculations\nof excitonic states and optical transitions by combining multiband <i><b>k</b></i>•<i><b>p</b></i> and\nconfiguration-interaction methods. We show that our design of structures\nprevents the generation of a considerable density of defects, as intended.\nThe emission of Si-based structures appears to be much broader than\nfor the reference dots, due to the creation of different QD populations\nwhich might be a disadvantage in particular laser applications, however,\ncould be favorable for others, e.g., in broadly tunable devices, sensors,\nor optical amplifiers. Eventually, we identify the overall most promising\ncombination of defect filtering layers and discuss its advantages\nand limitations and prospects for further improvements.