Selective area growth of InAs quantum dots with a metal mask towards optical integrated circuit devices

A metal-mask (MM) molecular beam epitaxy technique for selective-area-growth (SAG) of self-assembled InAs-quantum dots (QDs) on a GaAs substrate was developed for realizing ultra-small and ultra-fast all-optical switches (PC-SMZ). Growth conditions of the QD were optimized by virtue of the MM with a large window enabling real-time observations of reflection-high-energy-electron-diffraction patterns and growth temperatures. Successful SAG was confirmed by atomic force microscope observations of the high-density (4×10 10 cm -2 ) QD grown only on the unmasked area, while high uniformity of the QD was examined by room-temperature photoluminescence (PL) measurement. It resulted in a 1250 nm peak in the center wavelength, 38 meV in FWHM, comparable to that of the QD grown without the MM. In addition, insertion of a strain-reducing layer of GaInAs on the QD reported previously was confirmed to be effective for controlling the PL peak wavelength of the QD between 1250 and 1320nm without degrading the optical quality of QDs. The MM method shown here provides a possibility of an advanced PC-SMZ, i.e., an ultra-fast all-optical flip-flop (PC-FF), which requires a QD ensemble with a different absorption-peak wavelength in a different area.