**4.2. Self-assembly growth**

Self-assembly growth is one of the bottom-up methods. Molecular Beam Epitaxy (MBE) and Metal Organic Chemical Vapor Deposition (MOCVD) are widely used in the growth of the superlattice with different materials of different lattice constants.Semiconducting compound with a smaller lattice constant is grown (deposited atom by atom) on the surface of a com‐ poundwith a larger lattice constant. The relaxation of the grown layer after specific growth thickness due to lattice mismatch results in nucleation of islands of random shapes and controllable size. This growth mode is known as Stranski-Krastanov growth (see Figure 9).MBE method, beside it is sophisticated and slow, it is expensive. However, growth control of quantum dots is precise and multi-layers of quantum dots is possible. MOCVD is used in mass production of sample wafers and in contrast to MBE the growth of crystals is by chemical reaction and not physical deposition. In this approach high vacuum and temperature are required. Figure 9

**Figure 9.** Schematic of InAs island formation on GaAs surface by Stranski-Krastanow growth.
