Hiroshi Kukimoto

Metalorganic vapor phase epitaxy of low‐resistivity p‐type ZnSe

Low‐resistivity p‐type ZnSe layers have been successfully grown on GaAs substrates by metalorganic vapor phase epitaxy with the use of dimethylzinc and diethylselenide as source materials and lithium nitride as the dopant. The lowest resistivity achieved is 0.2 Ω cm, and the highest carrier concentration is 9×1017 cm−3. ZnSe p‐n diodes fabricated by this technique have shown blue emission; the spectral peak is located at 467 nm.

Coherent Growth of ZnSe on GaAs by MOCVD

The lattice parameters of ZnSe have been studied for epitaxial layers of different thicknesses grown on GaAs (100) substrates by metalorganic chemical vapor deposition (MOCVD) using dimethylzinc and diethylselenide as source materials. The results indicate that layers thinner than 0.15 µm can grow coherently on GaAs involving strains due to the lattice mismatch between ZnSe and GaAs, while thicker layers contain misfit dislocations introduced by the relaxation of strain.

Near‐band‐edge photoluminescence in ZnSe grown from indium solution

The near‐band‐edge photoluminescence of ZnSe crystals grown from an In solution has been studied in order to elucidate a transition mechanism of the room‐temperature blue emission band which is typically observed in the photoluminescence of the low‐resistivity ZnSe crystals and the electroluminescence of the ZnSe diodes of metal‐insulator‐semiconductor (MIS) structure. On the basis of the temperature‐dependent behavior of the various near‐band‐edge emission bands, i.e., changes in the peak energies and the intensities over the wide temperature range, the room‐temperature blue emission is attributed to the recombination between free holes and donor electrons. Special attention is paid to a relation between this emission and the low‐temperature exciton emission due to the recombination of excitons bound to the ionized donor.

Electroluminescence in hydrogenated amorphous silicon‐carbon alloy

White electroluminescence (EL) was observed for the first time in the hydrogenated amorphous silicon‐carbon alloy a‐SixC1−x: H(x=0.2–0.4) at room temperature. Experiments were carried out for the devices which consisted of an amorphous film sandwiched between two insulating layers of Y2O3. EL is observable above a threshold ac voltage of 100 V. The EL spectrum is slightly different from the photoluminescence spectrum of the amorphous film.

Growth kinetics in the MOVPE of ZnSe on GaAs using zinc and selenium alkyls

For the MOVPE growth of ZnSe on GaAs using zinc and selenium alkyls, the dependence of growth rate on growth temperature (Tg) and transport rate of source materials have been investigated. There have been observed two characteristic temperature ranges; i.e., a higher temperature range (500 < T < 600°C) where the growth rate is independent of Tg, and a lower temperature range (400 < Tg < 500°C) where the growth rate changes exponentially with temperature. The dependence of growth rate on the transport rate of various kinds of source materials including diethylzinc, dimethylzinc, diethyl selenide and dimethyl selenide clearly indicates that the growth at higher temperatures is characterized by the mass transport of Zn and Se sources and that at lower temperatures by a kinetic process occurring on the growth surface.

ZnS blue‐light‐emitting diodes with an external quantum efficiency of 5×10−4

ZnS diodes emitting a stable and bright blue light with forward biases above 5 V are investigated. The external quantum efficiency for the diode is as high as 5×10−4 at room temperature. The presence of a thin high‐resistivity ZnS layer on the low‐resistivity ZnS is essential for the present diode. The fairly high efficiency is accounted for by a relevant mechanism of the donor‐acceptor–pair emission.

The Local-Environment-Dependent DX Centers: Evidence for the Single Energy Level with a Specified Configuration

The energy-level structure of the DX centers corresponding to specific local environments was investigated under hydrostatic pressure. Several discrete DX levels, each of which was a well-defined single level, were clearly resolved. The energy level of the Si DX center surrounded only with Ga was determined to be 295 meV above the ?-conduction band edge of GaAs. When Al is coordinated as the 2nd-nearest neighbor, the energy level is lowered by as much as 120 meV. The energy level is sensitive not only to the number of Al 2nd-nearest neighbors, but also to the atomic configuration itself.

Alloy Fluctuation in Mixed Compound Semiconductors as Studied by Deep Level Transient Spectroscopy

Deep level transient spectroscopy (DLTS) has been utilized to detect alloy fluctuation around defects in several kinds of alloy semiconductors. An increased half-width in the DLTS spectrum has been observed in the ternary and quaternary systems of InGaP and InGaAsP whereas the binary systems of GaP and InP have not shown such broadening. The broadening can be interpreted as a fluctuation of defect properties due to the increased freedom of atom arrangements around the relevant defect in the alloy systems.

Erratum: White photoluminescence of amorphous silicon‐carbon alloy prepared by glow‐discharge decomposition of tetramethylsilane

An amorphous film of silicon‐carbon alloy with approximate composition Si0.1C0.9 was prepared on a fused‐quartz, a glass, or a silicon wafer by the glow‐discharge decomposition of tetramethylsilane. The film has an optical gap energy as large as 2.8 eV and shows white photoluminescence even at room temperature due to its broad emission band over the whole range of the visible spectrum. The photoluminescence is observable for the films deposited at substrate temperatures below 300 °C.

A Capacitance Investigation of InGaAs/InP Isotype Heterojunction

We have measured deep levels near the InGaAs/InP heterointerface by DLTS and C-V method. Three deep levels, E1, E2 and E3, have been found near the heterointerface, whose activation energies are 0.17 eV, 0.37 eV and 0.54 eV, respectively. The concentrations of E2 and E3 rapidly decrease when approaching the heterointerface from the InP, indicating that the two levels are located only in the InP substrate. The E1 level, on the other hand, can be found only near the heterointerface. The density of the E1 level is well correlated with the interface charge density which is determined by the C-V analysis. Both of the densities are dependent on the degree of the lattice mismatch between the InGaAs epitaxial layer and the InP substrate.