Keisuke Kobayashi

Structure study of Au–GaAs(001) interfaces by HEIS, XPS, and RHEED

MeV He+ ion scattering/channeling (HEIS), angle resolved XPS, and RHEED have been applied to study the Au and MBE‐grown GaAs(001)‐c(4×4) interface structures in the Au film thickness range of ≲70 A and the annealing temperature range from room temperature up to ∼300 °C. The results show release of the As atoms and epitaxial growth of the Au film even at room temperature. The shrinked Au film after annealing displays selective registry to the [110] direction, which is believed to result from a strong Au–GaAs(001) interaction.

Formation of InGaAs strained quantum wires on GaAs vicinal (110) substrates grown by molecular beam epitaxy

Abstract InGaAs quantum wires (QWRs) are naturally formed on GaAs vicinal (110) substrates by molecular beam epitaxy (MBE). These QWRs are induced by thickness modulation at coherently aligned giant step edges. Atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM) observations show the uniformity of giant steps and thickness modulation at giant step edges on GaAs vicinal (110) substrates. Photoluminescence (PL) measurements reveal that the PL spectra of InGaAs QWRs sample show lower energy shift as compared to those of InGaAs quantum well (QWL) on GaAs (100) substrates grown at the same time. This is consistent with the thickness modulation at the giant step edges. The PL observation evidences the carrier confinement in the QWRs.

Photoluminescence core-level excitation of CdSe quantum dot structures

Abstract We propose a new method of photoluminescence (PL) measurements, that is, exciting core levels using synchrotron radiation. This method has been applied to characterize CdSe quantum dot (QD) structures in this study. PL spectra of the CdSe QD sample under Zn 2p core-level excitation are slightly different from conventional PL. PL core-level excitation (PLCLE) spectra have sharp Zn 2p3/2 and Zn 2p1/2 absorption edges and core-exciton peaks for CdSe QDs. Moreover, the PLCLE spectra reveal interfacial states between ZnSe barrier layers and CdSe QDs. This result indicates that PLCLE is useful as a local probe for the thin films and semiconductor nanostructures.

Laser Cyclotron Resonance in n-Type Indium Antimonide under the Pulsed Electric Field

A CW laser cyclotron resonance in n-type indium antimonide is carried out with the modulation by pulsed electric fields. Through this method one can judge if a particular transition arises from the impurity ground state, thus facillitating the interpretation of the somewhat ambiguous spectra of the impurity cyclotron resonance. Some considerations on the electron distribution are made using the data obtained in the present experiment.

Photoluminescence inner core excitation in semiconductor quantum structures

Abstract We introduce a photoluminescence inner core excitation (PLICE) for the studies of semiconductor quantum structures. This novel method, in which we use synchrotron radiation as tunable excitation source, is expected to facilitate us to obtain electronic and compositional information about buried quantum structures. Here we report experimental results on quantum dots (QDs) and quantum wires (QWRs), in order to demonstrate potential applicability of the method to the semiconductor nanostructure studies.

Photoluminescence of InAs quantum wires on vicinal GaAs(110) surfaces

We have performed photoluminescence (PL) measurements of InAs quantum wires (QWRs) on vicinal GaAs(110) surfaces. Strongly polarized photoluminescence is observed for the InAs QWRs. At 140K, opposite polarization property is found in the vicinity of higher energy side than the peak energy of the QWRs. This result indicates that the opposite polarization property is due to light-hole transition.

Photoluminescence of modulation doped GaAs quantum wires on vicinal GaAs (110) substrates

Modulation-doped GaAs quantum wires are grown on the surfaces with giant steps which are naturally formed on vicinal GaAs (110) substrates by molecular beam epitaxy (MBE). It is found that photoluminescence (PL) peaks shift to lower energy with increasing doping level and to higher energy with increasing excitation intensity. These results indicate that the GaAs quantum wires are successfully modulation-doped.