Kuninori Kitahara

Selective growth of InP buried structure by chloride vapor phase epitaxy

Selective growth of an InP buried layer by In/PCl3/H2 vapor phase epitaxy was developed for buried layer GaInAsP/InP long wavelength laser diodes. For the first time, a completely flat‐surface buried layer was grown into grooves with good morphology on a (100) exactly oriented InP substrate, but not on a (100) 2° off oriented substrate. We found that the side of the groove was covered with a buried InP layer in the early stage of epitaxial growth. Therefore, the present selective growth would be effective for the protection of the interface between the active and buried layers from thermal degradation. The resistivity of InP, measured by using an n‐i‐n structure, was found to be higher than 103 Ωu2009cm at room temperature, which is sufficient for the buried layer of an usual laser diode.

Nonuniform photoluminescence intensity distribution on semi‐insulating GaAs and effects of Cr and dislocations

The nonuniformity of semi‐insulating GaAs is studied by the near‐band‐edge luminescence (PL) intensity profile along the diameter of circular wafers grown by the liquid encapsulated Czochralski technique. The shapes of the profiles depend on the location of the wafer in the ingots and on the density of Cr. Many sharp peaks are observed in the profiles of undoped and lightly Cr‐doped ingots but are suppressed by heavy doping of Cr. PL intensity is enhanced in the region where dislocation density is high. This correlation is explained by the interaction between the dislocation and the nonradiative center.

Current‐voltage characteristics and deep levels in chromium‐doped semi‐insulating GaAs

It is deduced from the correlation among current‐voltage characteristics, photoconductivity spectra, and Fermi‐level energy that the current‐voltage characteristics of chromium‐doped semi‐insulating GaAs are dominated by the concentration ratio of the deep level related with chromium to the deep level related with oxygen. This correlation is explained by a space‐charge‐limited current model.

CORRELATION BETWEEN ELECTRON MOBILITY AND SILICON-HYDROGEN BONDING CONFIGURATIONS IN PLASMA-HYDROGENATED POLYCRYSTALLINE SILICON THIN FILMS

This letter describes the relationship between electron mobility and Si-hydrogen bonding configurations in poly-Si thin films after plasma-hydrogenation treatment. A 50-nm-thick amorphous-Si film was crystallized by excimer laser irradiation followed by plasma hydrogenation. Measurements of the Hall effect and Raman scattering demonstrated that mobility increased under the Si-H dominant state and decreased under the Si-H2 dominant state, which were respectively caused by adjusted and excessive hydrogenation times. Mobility degradation was recovered by dissociation of excess H atoms by annealing. The origin of the correlation is discussed in terms of imperfections such as grain boundaries and in-grain defects.

A new GaAs on Si structure using AlAs buffer layers grown by atomic layer epitaxy

Abstract We have developed a new GaAs on Si structure with a thin AlAs buffer layer which was grown by atomic layer epitaxy (ALE). The characteristics of two types of ALE layers, GaAs and AlAs, were studied. We have found that single crystals of GaAs and AlAs layers can be grown directly onto Si substrates. Even though the growth was initiated by the formation of three-dimensional islands, AlAs layer growth changed from three-dimensional to two-dimensional at an earlier stage than that of GaAs layers. The morphology and quality of the ALE buffer layers are markedly improved by initiating the growth from AlAs. The characterization of GaAs layers grown by metalorganic vapor phase epitaxy on ALE layers indicates that the ALE-AlAs buffer layer will help improve the quality of GaAs on Si.

GaInP growth by chloride vapor phase epitaxy

Abstract GaInP layers were grown epitaxially on GaAs substrates by chloride vapor phase epitaxy (VPE). The dependence of morphology, photoluminescence characteristics on growth temperature and composition as well as doping with sulfur, selenium, and silicon were studied. We obtained high photoluminescence emission intensity from unintentionally doped crystals and high purity crystals with a narrow FWHM, 7.4 meV at 77 K (3.8 meV at 4.2 K). The background carrier concentration of undoped Ga 0.52 In 0.48 P was estimated to be 1 × 10 15 cm -3 using samples lightly doped with sulfur. We found that the best growth temperature for undoped Ga 0.52 In 0.48 P was 680°C, and that the best quality crystal was obtained not when GaInP was lattice matched to the GaAs substrate at room temperature, but when the composition of GaInP was on the InP side. Doping experiments were performed using H 2 S, H 2 Se, and SiCl 4 . GaInP electron carrier concentrations of 4 × 10 18 cm -3 were achieved by S and Se doping. When heavily doped with S and Se, the compositions of the epitaxial layers were shifted to the GaP side as compared to undoped samples grown under the same conditions. When SiCl 4 was used, high concentrations of Si were found at the interface between GaInP and GaAs. This appears to be due to the difference between the binding energy of chlorinated silane and As, and the binding energy of GaCl (or InCl) and As at the surface of the GaAs layer. Since the binding energy between the chlorinated silane and As is greater than the binding energy between GaCl (or InCl) and As, high concentrations of silicon appear at the interface between the GaInP epitaxial layers and the GaAs layer.

Chloride vapor phase epitaxial growth of high‐purity GaInP

High‐purity GaInP alloy was grown by chloride vapor phase epitaxy (Ga/In/PCl3/H2 system) with two separate metal source regions. The alloy composition could be precisely controlled by using separate regions for Ga and In metals. From the photoluminescence and Hall effect analysis, epitaxial layers lattice matched to GaAs substrates showed high emission efficiency, the full width at half‐maximum of the free‐exciton luminescence was as narrow as 7.4 meV at 77 K (3.8 meV at 4.2 K), and the low impurity concentration was below 1.5×1015 cm−3.

Chloride vapor phase epitaxial growth of a Ga0.52In0.48P/GaAs heterostructure with an abrupt heterointerface

Chloride vapor phase epitaxy of Ga0.52In0.48P/GaAs was studied using a reactor with two growth chambers. We have obtained high‐purity epitaxial layers of both GaInP and GaAs. For the growth of a heterostructure with an abrupt interface, the optimum growth condition was investigated in detail. Abruptness of the heterointerface was investigated by observing the two‐dimensional electron gas at the heterointerface of Ga0.52In0.48P/GaAs by the Hall and Shubnikov–de Haas measurements.

Transmission electron microscopic study of AlAs/Si heterostructures grown by atomic layer epitaxy

Abstract AlAs/Si heterostructures grown by atomic layer epitaxy have been evaluated by transmission electron microscopy. The heterointerface is found to be extremely abrupt compared to GaAs/Si heterostructures grown by metalorganic vapor phase epitaxy. It is also noted that atomic steps are clearly observed at the interface and that no amorphous or alloyed regions are found. At the initial stage of growth, a three dimensional island growth mode is dominant. However, two-dimensional growth takes place after depositing only 36 atomic layers of AlAs. Two types of defects are observed in the AlAs layer: stacking faults and microtwins. Although the density of these defects is high, they tend to self-annihilate at the interface between the AlAs layer and the Upper GaAs thick layer. These results lead us to conclude that using an AlAs layer grown by atomic layer epitaxy as a buffer layer is a promising way to achieve high-quality GaAs/Si heterostructures with a low defect density.

Growth of high resistivity GaAs VPE layers for device applications by the AsCl3-Ga-N2 system

High resistivity GaAs VPE layers with resistivities higher than 105 ohm cm have been successfully grown on Cr-doped semi- insulating substrates by the AsCl3-Ga-N2 system. It was found that the growth of high resistivity undoped GaAs VPE layers requires close compensation between donors and acceptors and that the close compensation can be achieved by the growth at lower temperature range of 660 to 680°C.