[5/23] The 2nd WPI-AIMR Joint Seminar in FY2014


The 2nd WPI-AIMR Joint Seminar in FY2014


From Superlattices to Quantum Dots:
A Perspective of Nanostructure Devices


Prof. Hiroyuki Sakaki
(Toyota Technological Institute and National Institute of Materials Science)


May 23 (Fri.), 2014 16:00-17:00


Seminar Room, 2nd floor, WPI-AIMR Main Bldg.


Thanks to advanced epitaxial technology, one can form a variety of layered nanostrcutures, such as quantum wells (QWs), superlattices (SLs), and selectively-doped heterojunctions. Two-dimen- sional (2D) carriers confined in such structures have been widely studied, because of their impor- tance both in 2D physics and advanced device applications, such as QW lasers and high-speed FETs.
To explore further potentials of nanostructures, the use of 1D and 0D electrons in quantum wires (QWRs) and quantum dots (QDs) was proposed to make such new devices [1] as planar SLs [2], QWR FETs [3], and QD lasers [4]. Though QWRs and QDs could not be initially made, these proposals spurred material scientists to develop new methods of nanostructure fabrication.
While electron-beam technique was used initially to form QWRs and QDs of around 100nm in size, several new methods have been developed to form 10nm-scale QWRs and/or QDs; they include the overgrowth of an n-AlGaAs on the cleaved edge of GaAs QWs and the facet-selective growth on patterned substrates [1]. It has been also found that 10nm-scale QDs can be formed by self-assem- bled Stranski-Krastanow (SK) growth on lattice-mismatched substrates and also by the droplet epitaxy, in which metallic droplets are formed and then transformed to QDs of intermetallic com- pounds [1]. The SK growth has been used to make QD devices, such as QD lasers of excellent tem- perature stability [5], single-photon emitters, and interband /intersubband QD photodectors [1].
It has been also shown that 10nm-scale QWRs and related nanostructures can be formed by such methods as the stacking of multiple SK QDs and the vapor-liquid-solid growth of nanowires on catalytic nanoparticles; these methods have been successfully used to make various QWR/QD based devices, such as QWR FETs, single-electron transistors, LEDs, photodetectors and so on. In this talk, we review recent advances in QD/QWR growth [6] and discuss their device prospects.


  • See for review, H. Sakaki: Tech. Digest of IEEE Int’l Electron Devices Meeting 9-16 (2007)
  • H. Sakaki, K. Wagatsuma, J. Hamasaki, and S. Saito: Thin Solid Films 36 (1976) 497.
  • H. Sakaki: Jpn. J. Appl. Phys. 19 (1980) L735.
  • Y. Arakawa and H, Sakaki: Appl. Phys. Lett 40 (1982) 939.
  • K. Otubo, 6 others, M. Sugawara, and Y. Arakawa: Jpn. J. Appl. Phys. Part II 43 (2004) L112
  • M. Ohmori, P. Vitushinskiy, and H. Sakaki: Appl. Phys. Lett. 98 (2011) 133109


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