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We report on the ability to grow InAs quantum dots (QDs) by droplet epitaxy (DE) using solid-source molecular beam epitaxy (MBE). In particular, the control of the size and density of InAs QDs at near room temperatures are achieved as a function of substrate temperature and crystallization condition. For a typical range of QD density ( ~109 to 1010 cm-2), the growth window is revealed to be fairly narrow ( ~20degC). In droplets are extremely sensitive to surface diffusion and arsenic background pressure even at near room temperatures. As a result, a very careful fabrication procedure is required to crystallize In droplets in order to fabricate desired shape of InAs QDs. For this purpose, we developed a double-step crystallization process, in which As background recovery and high-temperature crystallization are introduced. In addition, the results by DE are compared with QDs fabricated by Stranski-Krastanow (S-K) growth approach in terms of size and density. The results can find applications in optoelectronics as the fabrication of QDs by DE approach has more flexibility over S-K approach, i.e., more freedom of size and density control.
Date of Publication: July 2009