Guided assembly of quantum dots through selective laser heating

We report the self-assembly of InGaAs quantum dots (QDs) grouped along lines on semiconductor surfaces. Nanoscale spatial thermal modulations were created in-situ on strained-but-flat InGaAs surfaces in a Molecular Beam Epitaxy (MBE) growth chamber by employing interferential irradiations of high power laser pulses. As-irradiated surfaces were examined using an attached ultra-high vacuum Scanning Tunneling Microscope (STM). STM images indicate that the irradiation induces self-assembly of QDs. The average size of laser-induced QDs is smaller while their density is larger than that of QDs formed by the typical Stranski–Krastanov (S–K) growth mode. Furthermore, the dot density is modulated sinusoidally with a periodicity commensurate with that of the interference, which suggests that the placement of QDs can be controlled on the scale of the optical wavelength used.

► We examine the surface morphology modified by interferential irradiation of laser.
► Application of inferential laser pulses induces self-assembly of quantum dots.
► The dot density modulates with the same periodicity of the laser interference.
► Control of dot placement is possible via interferential irradiation of laser pulses.
► Use of a 7 ns laser pulse suggests that the atoms diffuse fast to form dots.