Akihiro Ohtake

Two types of structures for the GaAs(001)-c(4×4) surface

Scanning tunneling microscopy, reflectance difference spectroscopy, and x-ray photoelectron spectroscopy have been used to study the atomic structures of the As-stabilized GaAs(001)-c(4×4) surface. We found that the c(4×4) surfaces are classified into two phases of α (Ga–As dimer structure) and β (As–As dimer structure). While the α phase is obtained by heating the β phase under As fluxes, we found that the structural change from β to α is kinetically-limited.

Self-Assembly of Symmetric GaAs Quantum Dots on (111)A Substrates: Suppression of Fine-Structure Splitting

Great suppression of fine-structure splitting (FSS) is demonstrated in self-assembled GaAs quantum dots (QDs) grown on AlGaAs(111)A surface. Due to the three-fold rotational symmetry of the growth plane, highly symmetric excitons with significantly reduced FSS are achieved. Scanning tunneling microscopy and cross-sectional transmission microscopy demonstrate a laterally symmetric dot shape with abrupt interface. Polarized photoluminescence spectra confirm excitonic transition with FSS smaller than ~20 µeV, a substantial reduction from that of QDs grown on (100).

Nature and origins of stacking faults from a ZnSe/GaAs interface

Existence of ∼3–4 monolayers of Ga2Se3- and Ga2Te3-like interfacial layers are suggested by transmission electron microscopy of Se- and Te-exposed (or -reacted) ZnSe/GaAs interfaces, respectively. Densities of extrinsic Shockley- and intrinsic Frank-type stacking faults are of ∼5 ×107/cm2 in samples grown on Se- or Te-exposed GaAs surfaces. Annealing on the Se- or Te-exposed GaAs generated a high density of vacancy loops (⩾1×109/cm2) with an increase of the densities of both intrinsic and extrinsic-type stacking faults (⩾5×108/cm2) after growth of the films. Formation of the intrinsic stacking faults or vacancy loops and extrinsic stacking faults may be related to the presence of cation vacancies and interstitials, respectively, on the surface of the GaAs epilayer, due to the interaction between Se or Te and the GaAs epilayer with charge unbalanced Ga–Se or Ga–Te bondings. On the other hand, ∼2 and 3–4 monolayers of Zn–As interfacial layers are recognized in samples grown on Zn-exposed GaAs-(2×4) and -c(4...

In situ observation of surface processes in InAs/GaAs(001) heteroepitaxy: The role of As on the growth mode

Surface processes of the growing thin films of InAs on GaAs(001) substrates have been studied as a function of substrate temperature and As to In flux ratio. They have been observed by reflection high-energy electron diffraction and total-reflection-angle x-ray spectroscopy in real time. At temperatures lower than ∼480 °C, InAs grows in a Stranski–Krastanov mode irrespective of the As/In flux ratio, while the growth mode of InAs strongly depends on the flux ratio above ∼500 °C. We have found that the sticking probability of In decreases as the As flux is decreased above ∼500 °C, which results in the changes in the growth mode of InAs.

The role of zinc pre-exposure in low-defect ZnSe growth on As-stabilized GaAs (001)

Zinc coverage and the structures of Zn-exposed As-stabilized GaAs(001)-(2×4) and -c(4×4) surfaces have been studied using x-ray photoelectron spectroscopy and scanning tunneling microscopy in order to clarify the role of the Zn pre-exposure process in ZnSe growth on GaAs(001). Since Zn atoms stick on the GaAs-(2×4) surface even though their interaction is very weak, Zn may act as a balancer to form a neutral ZnSe/GaAs interface. Zn can also remove excess As atoms and make a “pure” (2×4) structure that is the only possible starting surface for low-defect ZnSe heteroexpitaxy on a GaAs(001) surface.

Structure analysis of the Ga-stabilized GaAs ( 001 ) − c ( 8 × 2 ) surface at high temperatures

The structure of the Ga-stabilized

Characterization and control of II-VI/III-V heterovalent interfaces

\mathrm{GaAs}(001)\ensuremath{-}c(8\ifmmode\times\else\texttimes\fi{}2)

Electrical characteristics and thermal stability of HfO2 metal-oxide-semiconductor capacitors fabricated on clean reconstructed GaSb surfaces

surface has been studied using rocking-curve analysis of reflection high-energy electron diffraction (RHEED). The

Reflection high-energy electron diffraction analysis of the InSb{111}A,B-(2 × 2) surfaces

c(8\ifmmode\times\else\texttimes\fi{}2)

Non-contact and non-destructive measurement of carrier concentration of nitrogen-doped ZnSe by reflectance difference spectroscopy

structure emerges at temperatures higher than 600 \ifmmode^\circ\else\textdegree\fi{}C, but is unstable with respect to the change to the