Monolithic Integration of AlGaAs Distributed Bragg Reflectors on Virtual Ge Substrates via Aspect Ratio Trapping

High quality AlxGa1-xAs distributed Bragg reflectors (DBRs) were successfully monolithically grown on on-axis Si (100) substrates via a Ge layer formed by aspect ratio trapping (ART) technique. The GaAs/ART-Ge/Si-based DBRs have reflectivity spectra comparable to those grown on conventional bulk off-cut GaAs substrates and have smooth morphology, and good periodicity and uniformity. Anitphase domain formation is significantly reduced in GaAs on ART-Ge/Si substrates, and etch pit density of the GaAs base layer on the ART-Ge substrates ranges from 10^5 to 6 x 10^6 cm^(-2). These results paved the way for future VCSEL growth and fabrication on these ART-Ge substrates and also confirm that virtual Ge substrates via ART technique are effective Si platforms for optoelectronic integrated circuits.