Kenji Momose

Dislocation-free and lattice-matched Si/GaP1−xNx/Si structure for photo-electronic integrated systems

We proposed a Si/III–V–N compound semiconductors/Si structure, which is applicable to optoelectronic integrated circuits (OEICs). The feature of this structure is that optoelectronic devices and Si electronic devices could be fabricated by low-temperature planar process at the same time. A dislocation-free and lattice-matched Si/GaP1−xNx/Si (x=2.9%) structure, which is a basic structure for OEICs, was grown by molecular-beam epitaxy. The images of transmission electron microscopy revealed that there were no threading dislocations and misfit dislocations in the epitaxial layers. It was clarified that the Si and GaP1−xNx layers were lattice-matched to Si and had structural high crystalline quality comparable to Si substrates.

Control of N Content of GaPN Grown by Molecular Beam Epitaxy and Growth of GaPN Lattice Matched to Si(100) Substrate

We investigate the N content of a GaPN epilayer grown on GaP(100) by radio-frequency molecular beam epitaxy under various growth conditions. It is found that the N content of GaPN increases with decreasing growth temperature and with increasing rf power of the nitrogen plasma source. The N content was controlled by means of the growth temperature and rf power, and the GaPN epilayer was grown on a Si(100) substrate with a thin GaP buffer layer. The epilayer is investigated by cross-sectional transmission electron microscopy and it is clear that misfit dislocations and threading dislocations are not generated in the GaPN epilayer. As a result, it is demonstrated that lattice-matched and defect-free GaPN epilayers can be grown on Si(100) with a thin GaP buffer layer. We also discuss the effect of N incorporation on the generation of dislocations.

Dislocation-free GaAsyP1−x−yNx/GaP0.98N0.02 quantum-well structure lattice- matched to a Si substrate

We report that a lattice-matched and dislocation-free GaAsyP1−x−yNx/GaP0.98N0.02 quantum-well (QW) structure can be grown on a Si substrate. A two-dimensional growth mode was maintained during growth of all the layers. It was confirmed that the QW structure was lattice-matched to the Si substrate from the lattice constant measured by x-ray diffraction. A cross-sectional image taken by transmission electron microscopy revealed that no threading dislocations or misfit dislocations were observed at the QW structure.

Hardening Effect of GaP1-xNx and GaAs1-xNx Alloys by Adding Nitrogen Atoms

We investigated the strain relaxation process of GaP1-xNx/GaP and GaAs1-xNx/GaAs in order to clarify their mechanical characteristics by adding nitrogen atoms. It was observed by transmission electron microscopy (TEM) that the critical thicknesses were greater and the generation rates of the misfit dislocations were slower in the GaP1-xNx and GaAs1-xNx layers than those in the GaP layer with a similar lattice mismatch. The critical thickness of the GaAs1-xNx layer was greater than that of the GaP1-xNx layer for the same nitrogen composition of 2%. The direction of higher crack density was orthogonal to that of the higher misfit dislocation density. These results indicate that the propagation of dislocations is prevented in III–V–N alloys such as GaP1-xNx and GaAs1-xNx, so that these alloys are harder than III–V compounds that lack nitrogen atoms. This feature could be attributed to the dislocation pinning and alloy hardening effects due to nitrogen atoms.

Control of growth process and dislocation generation of GaAs1−xNx grown by all-solid-source molecular beam epitaxy

We investigated the growth process and dislocation generation of GaAs 1-x N x alloys grown on GaAs by solid-source molecular beam epitaxy (MBE). It was found that the GaAs 1-x N x alloys with a mirror-like surface can be grown by lowering the arsenic-to-gallium flux ratio compared to that in the growth of GaAs. The nitrogen composition in the GaAs 1-x N x alloys increased with decreasing substrate temperature and with increasing RF-power. As the nitrogen composition increased, the misfit dislocations were observed at the GaAs 1-x N x -GaAs heterointerface. It was clarified that the propagation of dislocations was suppressed in GaAs 1-x N x alloys by adding nitrogen.

Improvement of crystalline quality of GaAsyP1−x−yNx layers with high nitrogen compositions at low-temperature growth by atomic hydrogen irradiation

Abstract We proposed a growth technique for III–V–N alloys with high quality and nitrogen composition, which was the low-temperature growth under atomic hydrogen irradiation. In the growth of GaPN, nitrogen compositions higher than 6% were obtained at growth temperatures lower than 350°C. GaAsPN alloys grown on GaP substrates were examined using X-ray diffraction and transmission electron microscopy. It was found that structural crystalline quality of a GaAs y P 0.93− y N 0.07 layer grown at 350°C was improved by atomic hydrogen irradiation. Photoluminescence was obtained from a GaAs 0.33 P 0.60 N 0.07 /GaP double heterostructure lattice matched to a GaP substrate.

High-Quality GaAsxP1-x/In0.13Ga0.87P Quantum Well Structure Grown on Si Substrate with a Very Few Threading Dislocations

We proposed a novel quantum well (QW) structure of GaAsxP1-x/In0.13Ga0.87P grown on a GaP/Si substrate with a small lattice mismatch (1.4%) to the Si substrate, for a highly reliable laser diode (LD) on a Si substrate, and attempted to form the structure with a GaAs0.68P0.32 well and GaAs0.27P0.73 guiding layers. A two-dimensional (2D) growth mode was maintained during the growth of all layers. A cross-sectional image taken by transmission electron microscopy (TEM) revealed that the density of threading dislocations is the lowest in light-emitting device structures grown on Si substrates, as far as we know. The lattice mismatch of 1.4% was accommodated at the In0.13Ga0.87P-GaP and the GaP-Si heterointerfaces by introducing misfit dislocations. The quality and structural profile of GaAsxP1-x epilayers was improved by varying the As4 flux in a short period. As a result, strong band-edge emission was observed from the GaAs0.68P0.32 QW at room temperature (RT). It was also found by secondary-ion mass spectroscopy (SIMS) that relatively abrupt heterointerfaces were formed in the QW structure of GaAs0.68P0.32/GaAs0.27P0.73/In0.13Ga0.87P.

Study of the crystal quality and Ga-segregation in ZnSe films grown by molecular beam epitaxy on AlxGa1−xAs and InxGa1−xAs buffer layers on GaAs substrates

Abstract In the present work, we report a study of the molecular beam epitaxial growth of ZnSe on GaAs substrates using Al x Ga 1− x As and In x Ga 1− x As ternary alloys as buffer layers. When growing ZnSe directly on a thermally desorbed GaAs substrate, surface segregation of Ga across the film towards the ZnSe surface was observed by secondary ion mass spectroscopy. We demonstrate that the use of AlGaAs buffer layers is very effective to suppress the Ga surface segregation. The characterization of the films by reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy, photoluminescence and photoreflectance spectroscopy revealed that the best crystal quality ZnSe films were obtained for buffer layers with In or Al concentrations of 1%.

Improvement of crystalline quality of GaAs/sub y/P/sub 1-x-y/N/sub x/ layers with high nitrogen compositions by low-temperature growth under atomic hydrogen irradiation

We have realized the dislocation-free and lattice-matched Si/GaP/sub 1-x/N/sub x//Si (x=2.9%) structure for optoelectronic integrated circuits (OEICs). The GaPN layer lattice-matched to Si showed luminescence with a peak wavelength of about 660 nm at RT. It is particularly required to find out the growth techniques which increases the nitrogen composition of III-V-N alloys in order to form an active layers with various wavelengths on Si substrates. However, crystalline quality has tended to be degraded with the increase in nitrogen compositions. Thus, we tried to grow the high quality III-V-N alloys with high nitrogen compositions at low temperature under atomic hydrogen (H) irradiation by solid-source molecular beam epitaxy.