Mitsuo Yoshikawa

Continuous operation over 1500 h of a PbTe/PbSnTe double-heterostructure laser at 77 K

Continuous operation over 1500 h at 77 K has been achieved by use of a PbTe/Pb0.93Sn0.07Te double‐heterostructure laser which was grown using the liquid‐phase‐epitaxy method. The cw threshold current changed only about 3% during the first 200 h. It is concluded that the lifetime of PbTe/PbSnTe double‐heterostructure lasers at 77 K is fundamentally very long.

Dislocations in Hg1−xCdxTe/Cd1−zZnzTe epilayers grown by liquid‐phase epitaxy

Misfit and threading dislocations in HgCdTe epitaxial layers grown on (111)B CdTe and CdZnTe substrates by liquid‐phase epitaxy have been investigated quantitatively by the etch pitting technique. In the HgCdTe/CdTe heterojunction, it has been found that the misfit dislocations introduced at the initial stage of epitaxial growth move to the 〈111〉 direction and distribute in such a way that they completely accommodate the mismatching strain of the compositional gradient caused by the Hg‐Cd interdiffusion. On the other hand, in HgCdTe/CdZnTe heterojunctions, misfit dislocations were found to be pinned by Zn out‐diffused from the substrate. For a proper ZnTe mole fraction in the CdZnTe substrate, the linear dislocation‐pit density on the (110) cleaved and etched surface was confirmed to decrease to about 1% of that using a CdTe substrate. It has also been found that the density of dislocations threading into the epitaxial layer was determined not by the magnitude of lattice mismatch, but by the dislocation ...

Misfit dislocations in PbTe-PbSnTe heterojunction

Abstract Misfit dislocations at the heterojunction of PbTe-PbSnTe layers grown by liquid phase epitaxy have been investigated by etch pit studies. The linear density of misfit dislocations along the 〈100〉 direction parallel to the heterojunction was in good agreement with the predicted value. This agreement indicates that the strain due to lattice mismatch between PbTe and PbSnTe is completely relieved by the introduction of misfit dislocations. It has been shown from the distribution of etch pits, electron probe analysis, and calculations, that the misfit dislocations spread around the heterojunction in the region determined by Sn self-diffusion during epitaxial growth.

Dislocations in HgCdTe-CdTe and HgCdTe-CdZnTe heterojunctions

Abstract Mechanisms that govern the generation and movement of dislocations in (111) heterojunctions of HgCdTe-CdTe and HgCdTe-CdZnTe grown by liquid phase epitaxy have been investigated with etch pit studies. The density and distribution of the misfit dislocations in these heterojunctions have been measured quantitatively and analyzed to clarify the mechanisms that generated them. The origins of the dislocations threading through the epilayer are also reported.

Domain structures of CdTe layers grown by MOCVD on offset-angle sapphire substrates

Abstract Single-domain CdTe layers are grown on offset-angle sapphire substrates by MOCVD, but showed a twinned structure on precise (0001)-oriented sapphire substrates. To estimate the offset-angle range at which single-domain growth is possible, CdTe layers were grown at 380°C with a [DETe]/[DMCd] ratio of 15 on (0001)-oriented sapphire substrates with a spherical surface. The offset-angle range for single-domain CdTe layers is between 0.1° and 7° on spherical substrates. Twinned structures were shown for substrates with an offset angle under 0.1° and polycrystalline CdTe was grown for substrates with offset angles above 7°. Single-domain CdTe layers were also grown over the entire area of flat-surface wafers with an offset angle of 3°. A model is proposed to explain the mechanism for single-domain formation on offset-angle substrates. The model is based on the lateral growth on a vicinal surface and the rearrangement of twinned domains in initial growth stages.

Heterointerface morphology of Pb1-YSnYTe-Pb1-XSnXTe (X, Y ⪅ 0.3) double heterostructure (DH) grown by LPE

The heterointerface morphology of Pb1-YSnYTe-Pb1-XSnXTe (X, Y ⪅ 0.3) DH grown by LPE has been investigated. The heterointerfaces of Pb0.93Sn0.07Te-Pb0.85Sn0.15Te DH are flat, and those of Pb0.87Sn0.13Te-Pb0.75Sn0.25Te DH are rough under the usual equilibrium cooling growth conditions. It has been found that this roughening phenomenon occurs because the melt and the epitaxial layer at the interface deviated much from equilibrium when the melt was slid on the substrate. There are two ways to get flat interfaces with an active layer composition about X = 0.25. One is to grow layers under supercooled conditions. The other is to reduce the compositional difference between the active and the two confining layers.

Antiphase Domain Structures of CdTe on Sapphire Substrates

Antiphase domain (APD) structures have been discovered in CdTe layers grown on (0001) sapphire substrates by MOCVD. To explain APD formation, an obstruction model based on a surface-reaction mechanism has been proposed. The proportion of one-phase domains to the total area varies with the [DETe]/[DMCd] ratio (VI/II ratio). A single-domain CdTe layer can be obtained at a VI/II ratio of 5. The APD structure shows a strong correlation with the crystallinity measured by X-ray. For a single-domain CdTe epilayer, theFWHM of the X-ray rocking curve shows 114 arc seconds and the EPD is 6× 10 cm −2

LATTICE MATCHING IN HgCdTe-CdZnTe HETEROJUNCTIONS

An etch pit study has been made on misfit dislocations in (111) HgCdTe-CdZnTe heterojunctions grown by liquid phase epitaxy. It was shown that misfit dislocations were localized at the original surface of the substrate, because Zn diffused into the epilayer during epitaxial growth prevents movement of dislocations. For lattice matching between Hg 0 7 Cd 0.3 Te and Cd 1−y Zn y Te, the optimum ZnTe mole fraction of Cd 1−y Zn y Te was found to be 2.9%.