Selective-area-growth of InAs-QDs with different absorption wavelengths via developed metal-mask/MBE method for integrated optical devices

The selective-area-growth (SAG) of InAs quantum dots (QDs) with different emission wavelengths on different areas was carried out using the metal-mask (MM) method during conventional molecular beam epitaxy (MBE) growth. Two SAG areas (SAG-1 and SAG-2) of the QDs were obtained using the rotational MM having square windows; first, the MM was mounted on a substrate for SAG-1, and then the same MM was used for SAG-2 after being rotated it by 180°. The absorption wavelengths of the selectively grown QDs were controlled by inserting strain-reducing layers of a different thickness on each grown QD layer. Photoluminescence measurements revealed the successful SAG of QDs in the neighboring a few hundred-micron-square areas with different emission wavelengths, e.g., 1250 and 1300 nm. These techniques are promising for applications of QD-based optical and electronic devices, including our proposed photonic crystal (PC) and QD-based all-optical digital flip–flop (FF) device, i.e., PC-FF.