Time-resolved photoluminescence characterization of InGaAs/GaAs nano-ridges monolithically grown on 300 mm Si substrates

The monolithic growth of IIIU+2013V materials directly on Si substrates provides a promising integration approach for passive and active silicon photonic integrated circuits but still faces great challenges in crystal quality due to misfit defect formation. Nano-ridge engineering is a new approach that enables the integration of IIIU+2013V based devices on trench-patterned Si substrates with very high crystal quality. Using selective area growth, the IIIU+2013V material is deposited into narrow trenches to reduce the dislocation defect density by aspect ratio trapping. The growth is continued out of the trench pattern and a box-shaped IIIU+2013V nano-ridge is engineered by adjusting the growth parameters. A flat (001) GaAs nano-ridge surface enables the epitaxial integration of a common InGaAs/GaAs multi-quantum-well (MQW) structure as an optical gain medium to build a laser diode. In this study, a clear correlation is found between the photoluminescence (PL) lifetime, extracted from time-resolved photoluminescence (TRPL) measurements, with the InGaAs/GaAs nano-ridge size and defect density, which are both predefined by the nano-ridge related pattern trench width. Through the addition of an InGaP passivation layer, a MQW PL lifetime of up to 800U+2009ps and 1000U+2009ps is measured when pumped at 900U+2009nm (only QWs were excited) and 800U+2009nm (QWsU+2009+U+2009barrier excited), respectively. The addition of a bottom carrier blocking layer further increases this lifetime to U+223C2.5ns (pumped at 800U+2009nm), which clearly demonstrates the high crystal quality of the nano-ridge material. These TRPL measurements not only deliver quick and valuable feedback about the IIIU+2013V material quality but also provide an important understanding for the heterostructure design and carrier confinement of the nano-ridge laser diode.

Publication year:2020