We report on the compositional and optical investigation of InGaAs(N) alloy films grown on GaAs (001) substrates by low-pressure (60 Torr) metalorganic vapor phase epitaxy (MOVPE). The alloy films with the room-temperature photoreflactance (PR) signal (Eo transition) wavelength range of 0.98–1.36 m have been grown. The variation in PL characteristics of the InGaAs(N) alloy films has been investigated as a function of alloy composition, excitation power and temperature. At low temperatures (T<100K), the PL spectra with several sub-peaks include localization emission as well as near-band-edge emission. On the other hand, the room-temperature PL properties for InxGa1-xAs1-yNy (x = 10.5% and 17.0% and y < 2%) are excellent with a single near-band-edge emission peak corresponding to their own Eo transition. The evolution of PL spectra with excitation power and temperature led to an insight into the nature of the near-band-edge states. The temperature dependence of integrated PL intensity indicates the presence of a large density of non-radiative recombination centers, showing a behavior characterized by two activation energies. Our results suggest that the origin of localization in InGaAsN alloy films is the alloy inhomogeneities of both In and N, which may results in the characteristic carrier dynamics.

The morphology and the atomic structure of a hexagonal gallium nitride (h-GaN) grain boundary was investigated employing a conventional TEM and an atomic resolution high voltage transmission electron microscope (ARHVTEM).

GaN was grown on a patterned GaAs (001) substrate by the metalorganic vaporphase epitaxy (MOVPE) method using selective area growth (SAG) and epitaxial lateral overgrowth (ELO) process. The pattern mask was aligned along [110] direction of the GaAs (001) substrate. Cubic GaN (c-GaN) grew in the window of the patterned substrate. h-GaN was nucleated on the {111} plane of the c-GaN and grew in the lateral direction to fabricate a grain boundary in the halfway between two masks. The resulting symmetric tilt grain boundary was a Σ 9 CSL boundary. The boundary plane was in most cases parallel to the {3308} plane. Structural analysis revealed that the boundaries consist of ordinary 6-memebered rings and some 5-membered and 7-membered rings. Additionally, the expected atomic bonding angle deviates from the experimental findings. The different bonding angle was attributed to contributions of ionic bonding in GaN.

Anisotropic X-Ray diffraction (XRD) and transport properties of cubic GaN grown on GaAs substrates correspond to the features of low-temperature grown GaN (LT-GaN) buffer layer. When the LT-GaN layer is grown on the surface tilted from (001) to [1-10] with annealing in arsenic ambient, the macroscopic step edges along [1-10] direction are modified by either the ambient of thermal annealing, or substrate misorientation. A parallel conduction in GaN, GaAs, and GaN/GaAs hetero-interface was observed by photoconductivity measurements. Transmission electron microscope (TEM) observation shows that self-annihilations for (-111) B stacking faults are preferentially occurred near GaAs interface when GaN film grown on the surface tilted from (001) toward [1-10] (As step edge) is annealed in arsenic ambient. TEM observation also shows that stacking faults and dislocations are preferentially generated near GaN/GaAs interface. It is suggested that anisotropic transport properties correspond to the well-like potential generated by band bending at GaN/GaAs interface. The nearly isotropic mobility of 3,000 cm2/Vsec at 77K is obtained by improving interface property.

GaP1-x-yAsyNx. (x ∼,2.3%, 0< y <19%) quaternary alloy semiconductor films on GaP substrates have been successfully grown by metalorganic vapor phase epitaxy (MOVPE). With the fixed supplies of trimethylgallium(TMG), AsH3 and dimethylhydrazine(DMHy) during the growth, the As concentration in the solid increased with increasing AsH3 supply, while the N concentration was almost unaffected. It has been demonstrated that the crystalline quality of the alloy films is much improved with the close lattice-matching to the GaP substrate, giving a superior surface morphology without any cross-hatches, a much narrower x-ray diffraction linewidth, and a significantly higher photoluminescence(PL) intensity.