Self-assembled formation of ZnCdSe quantum dots on atomically smooth ZnSe surfaces on GaAs(001) by molecular beam epitaxy

We investigate growth conditions to obtain atomically flat ZnSe film surfaces on GaAs(001) without forming ZnSe-related dot structures. It is found that high temperature growth is favorable for the growth of ZnSe with a smooth surface. In order to prevent degradation of interface properties at high substrate temperature, two-step growth of ZnSe layers is employed, where a low-temperature growth step is followed by high temperature growth. The two-step process enables one to grow ZnSe with atomically flat surface without ZnSe-related dots structures. The formation of self-assembled ZnCdSe quantum dots (QDs) is achieved on such atomically surfaces. Typical QD size is: base diameter of 21±3 nm and height of 8±2 nm. Even at a total deposition of ZnCdSe of 3.5 monolayer (ML), the QD density is as low as approximately 2.4 μm^-2. It is found that these QDs are formed on a ZnCdSe wetting layer whose thickness is at least 3 ML.