Taneo Nishino

Influence of growth temperature on crystalline structure in Ga0.5In0.5P grown by organometallic vapor phase epitaxy

The relation between growth temperature and ordered structures in Ga0.5In0.5P grown using organometallic vapor phase expitaxy is investigated using transmission electron diffraction, electroreflectance, and Raman scattering measurements. It is found that generation of the ordered structure is not related to the immiscibility of this alloy and that the ordered structures do not simply represent ‘‘sublattice ordering.’’ The anomalous band gap may be a consequence of the variation in the atomic arrangement of neighboring atoms, but not of the long‐range ordered structure itself.

Anomalous temperature dependence of the ordered Ga0.5In0.5P photoluminescence spectrum

The temperature dependence of the photoluminescence spectrum of Ga0.5 In0.5 P/GaAs grown by organometallic vapor phase epitaxy is measured. Samples with a highly long‐range ordered structure show anomalous behavior, where peak energy changes with temperature exhibiting Z‐shape dependence. In the range between 100 and 30 K, peak energy decreases monotonously with decreasing temperature, and below 30 K, begins to increase, splitting into two peaks. The most probable cause of this behavior is crystal defects related to the long‐range ordered structure.

Crystalline and electronic energy structure of OMVPE-grown AlGaInP/GaAs

Abstract The crystalline and electronic energy structure of AlGaInP/GaAs grown by organometallic vapor phase epitaxy (OMVPE) is investigated using transmission electron microscopy (TEM) and electroreflectance (ER), as well as photoluminescence (PL) and Raman scattering measurements. In TEM observation, sharp superstructure spots at the h+ 1 2 , k− 1 2 , l± 1 2 position, corresponding to CuPt type structure, are present in the (110) diffraction pattern. Based on this observation, the relationship between the bond and the ordered structure configuration on 9001) growth surface is discussed. It is also found by photoluminescence and Raman scattering measurements that the GaInP grown on (111)B is in a disordered state. Photoluminescence measurement for AlGaInP grown under various conditions shows that an ordered structure exists not only in GaInP but throughout the entire compositional range of the AlGaInP/GaAs. The electroreflectance spectrum shows anomalous structures specific to OMVPE-grown GaInP. The structures around 2.2 and 2.4 eV suggest that there exist additional interband transition edges caused possibly by zone-folding from the L point to the Γ point.

Electroreflectance study of ordered Ga0.5In0.5P alloys grown on GaAs by organometallic vapor phase epitaxy

We have measured the electroreflectance spectra of ordered Ga0.5In0.5P alloys grown on GaAs by organometallic vapor phase epitaxy. As a result, it has been found that there exist anomalous structures in the region of the E0 and E1 band edges of this material. These anomalous structures are closely related to the recently reported ordered phase in this alloy, since these structures have never been observed with disordered Ga0.5In0.5P alloys such as bulk crystals and epitaxial layers grown by liquid phase epitaxy.

Oxygen-Related Donors Stable at 700–800°C in CZ–Si Crystals

A variety of silicon-oxygen clusters have been induced in CZ–Si crystals by multi-step annealing at temperatures between 450 and 800°C. Five-step annealing (450°C, 100 h+500°C, 40 h+600°C, 20 h+700°C, 20 h+800°C, 20 h) has generated oxygen-related donors at a concentration of more than 1015 cm-3. The silicon-oxygen clusters were investigated using infrared absorption, resistivity, photoluminescence and TEM. In carbon-lean CZ–Si crystals, oxygen-related donors, which are stable at 700–800°C, were found to be related to both oxygen clusters nucleated at dislocation dipoles and to the so-called thermal donors. However, in carbon-rich CZ–Si crystals, oxygen-related donors, which are stable at 700–800°C, were related to oxygen clusters nucleated at carbon atoms, which can gather many oxygen atoms without forming dislocation dipoles.

Optical anisotropy of orthorhombic InS

Abstract The optical anisotropy of InS single crystals in the range of photon energy from 1.8 to 3.5 eV has been studied by absorption, electroreflectance and wavelength-derivative reflectance measurements. These systematic optical measurements for the polarizations, E // a and E // b , have revealed that the transition at the fundamental absorption edge of InS is allowed for E // b , and there exist three distinct doublet transitions having different selection rules in the photon energy region from 2 to 3.5 eV; Bo and B 0 doublet allowed only for E // b , A 0 and A 0 allowed only for E // a , and E 1 and E 1 allowed for both polarizations. The observed results are discussed based on the anisotropic nature of two chemical bonds in InS, cation-cation and cation-anion.

Electroreflectance of p-type GaAs

The electroreflectance spectra of p-type GaAs in photon energies from 1.3 to 3.5 eV have been investigated at temperatures from 300° down to 25°K. Measurements of electroreflectance have been performed by the method using the interface potential of GaAs-SnO2 heterojunction. Both signals of an exciton and the fundamental edge have been separated in the low temperature spectra, and an additional structure which may be associated with a localized state has been also observed below the fundamental edge. The similar structures with weak intensity appear near the spin-orbit split off edge. The line shapes of electroreflectance spectra which are related to Λ3−Λ1 transition and its spin-orbit split off edges are explained by the mixed electro-optical spectra of M1(⊥) and M1(∥) type critical points including the effect of thermal broadening. A method of estimating the thermal broadening factor from the temperature dependences of the electroreflectance spectra associated with Λ3−Λ1 transition edge is also presented.

Characterization of the optical properties of LPE InxGa1−xAsyP1−y thin layers grown on InP

Abstract A series of In x Ga 1− x As y P 1− y single-crystal thin layers have been grown on an InP substrate in a vertical liquid phase epitaxy furnace with a rotating slide boat system. The optical properties of these LPE quaternary alloys lattice-matched to InP have been investigated mainly by photoluminescence and electroreflectance measurements. Photoluminescence spectra of In x Ga 1− x As y P 1− y epitaxial layers are dominated by a strong luminescence line due to band-edge emission. At low temperatures, around 4.2 K, we have observed complicated luminescence bands with many fine structures. Electroreflectance spectra for the LPE In x Ga 1− x As y P 1− y layers are sufficiently broad to fulfil the low-field condition, and the analysis enabled us to determine precisely the band gap energy.

Electroreflectance of In0.79Ga0.21As0.54P0.46

We have measured Schottky‐barrier electroreflectance spectra of an In0.79Ga0.21As0.54P0.46 LPE layer at 81 K. Analysis of the spectra has enabled us to determine the interband reduced mass of the quaternary alloy together with the values of the band gap and spin‐orbit splitting. The obtained reduced mass μ=0.033m0, in agreement with the value calculated from interpolations of the accepted values for the related binary compounds.

Photoluminescence study on local atomic arrangements in InGaP and GaAsP alloys using Co deep impurity

Low‐temperature photoluminescence (PL) related to Co deep impurities in In1−x GaxP (0.74≤x≤1) and GaAs1−x Px (0.65≤x≤1) alloys has been studied. Broad PL bands with some structures have been observed in the 2.3‐μm region for both the alloys. The results of time‐resolved PL measurements have shown that the PL bands are due to the intracenter transitions 4T2(4F)→4A2(4F) in a substitutional Co2+ ion in the zinc‐blende lattices. These Co‐related PL spectra have been analyzed in terms of the local atomic arrangements around the Co luminescent center. As a result, it has been found that these Co‐related PL spectra in InGaP and GaAsP alloys are composed of several bands closely related to the local arrangement of atoms around the Co center.