Si doped and un do ped cubic GaN were grown by low pressure metalorganic vapor phase epitaxy using a two step growth process. After the deposition of a 20nm thick buffer layer, an about 1μm thick Si doped cubic GaN epitaxial layer was deposited. Doping l evel was determined by secondary ion mass spectroscopy measurements. X ray diff raction and photoluminescence measurements were used to characterize the str uctural and optical quality of the undoped and the Si doped cubic GaN.

A GaN intermediate protection layer, inserted between the low-temperature-grown buffer layer and the high-temperature-grown GaN epilayer, was used for growing cubic GaN on GaAs (1 0 0) substrates by metalorganic vapor-phase epitaxy. The intermediate protection layer was grown at moderate temperatures to prevent GaAs substrate from thermal decomposition. This technique enables us to grow cubic GaN on GaAs substrates at higher growth temperatures. Even at the growth temperature of high as 980°C, the interface between GaN layer and GaAs substrate is still smooth owing to the introduction of the intermediate protection layer. Photoluminescence and X-ray diffraction measurements showed that the crystal quality of the cubic GaN layer was improved by the realization of high-temperature growth using an intermediate protection layer.

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.

We present the fabrication and characterization of nonintentionally doped GaN and GaN:Mg Schottky metal–semiconductor–metal (MSM) photodetectors, grown on sapphire by metalorganic chemical vapor deposition. Low-leakage, Schottky contacts were made with Pt/Au. The devices are visible blind, with an ultraviolet/green contrast of about five orders of magnitude. The response times of the MSM devices were <10 ns and about 200 ns for GaN and GaN:Mg, respectively. The noise power spectral density remains below the background level of the system (10−24 A2/Hz) up to 5 V, for the undoped GaN MSM detector.

Selective growth of cubic GaN on patterned GaAs substrates was studied. The structural and morphological properties of cubic GaN are very dependent on the orientation of the mask stripes. Tn the case of window stripe opening along [011] direction, (111)B facets were clearly observed in all the samples, regardless of the different growth time. Both X-ray diffraction and photoluminescence measurements showed that the hexagonal phase GaN was considerably incorporated in the cubic GaN layer, indicating that the hexagonal GaN is easily constructed along-the (111)B facet. In contrast, window stripes opening along [01-1] direction resulted in the:formation of (311)A facets and subsequently a relatively flat surface occurred as the growth proceeded.-Strong emission peaks of cubic GaN were observed in the photoluminescence spectra.

Chemical vapor deposition (CVD) W plugs have been widely used for device metallization with excellent conformity in small contacts/vias with high aspect ratio [J. E. J. Schmitz, Chemical Vapor Deposition of Tungsten and Tungsten Silicides (Noyes, 1991)]. However, some unexpected plug fill such as plug loss and key hole exposing post tungsten chemical mechanical planarization (WCMP) still happened while going to smaller plug size and using metalorganic chemical vapor deposition (MOCVD) TiN barrier. In this study, MOCVD TiN and CVD W fill followed by WCMP for plug metallization were investigated. Extensive analysis had been conducted on various types of defective W plugs. Organic contaminants (hydrocarbon by-products) in MOCVD TiN deposition would prevent W deposition taking place inside the plug. For W wise, lower process temperature, carefully adjusted WF6/SiH4 and WF6/H2 partial pressure ratios had demonstrated better plug fill and electrical performance [T. E. Clark et al., J. Vac. Sci. Technol. B 9, 1478 (1991)]. In the WCMP approach, the effects of different oxidizer concentration in slurry were characterized. Eliminating the seam formation during the CVD W process can help avoid slurry attack in WCMP. The optimized integration scheme of MOCVD TiN barrier, CVD W, and WCMP was successfully achieved and is applied on 0.20 μm Logic production.

The metalorganic vapor phase epitaxial (MOVPE) growth of cubic GaN layers on misoriented GaAs (001) substrates, the faces of which were tilted from (001) toward [11-0] or [110] by 4°, was performed in order to investigate the effect of the substrate misorientation on the inclusion of hexagonal phase in the cubic GaN layer. The sample grown on the tilted surface toward [11-0] showed an enhanced generation of the hexagonal domain on the (11-1) face, whereas the hexagonal domain on the (1-11) face was suppressed. The sample grown on the tilted surface toward [110] showed the generation of the hexagonal domains on both the (11-1) and (1-11) faces with an equal magnitude. It is suggested that the generation of hexagonal domains may be suppressed when the exposure of the (11-1) or (1-11) faces by the thermal damage of the substrate surface is reduced.

We report on the growth of high quality cubic GaN films on GaAs (100) substrates by low pressure metalorganic vapor phase epitaxy. The GaN films exhibit a smooth surface which is free from cracks. X-ray diffraction shows the cubic nature of the GaN films. X-ray rocking curve with ω scan shows that the crystal quality of GaN films improves markedly with increasing growth temperatures. Photoluminescence measurements confirm the high quality of the cubic GaN films. The full width at half maximum of excitonic emission from the cubic GaN films is as narrow as 70 meV at 300 K.

Pb(Zr,Ti)O3 (PZT) films were deposited on cubic GaN/(100)GaAs for the first time with or without MgO buffer layer by pulsed laser ablation. MgO films were grown on cubic GaN with cube-on-cube epitaxy. It was found that MgO buffer layer is very useful for suppressing the diffusion of O and metal elements into GaN layer. Preferentially [100]-oriented perovskite PZT films were obtained on cubic GaN with MgO buffer layer although randomly oriented perovskite PZT films were obtained without MgO buffer layer. PZT/MgO/GaN structure is one of the promising candidates for integrated devices composed of ferroelectric waveguides and blue laser diodes.

Cathodoluminescence (CL) and photoluminescence (PL) investigations of single crystal GaN grown on 3C-SiC(100) substrates by metalorganic vapor-phase epitaxy are reported. The GaN grown on 3C-SiC substrates shows distinct crystal facets. We identified the square facet and inclined facet as cubic GaN and hexagonal GaN, respectively. We studied the luminescence properties from the square facet or from the inclined facets separately by CL. For the cubic GaN, a sharp excitonic transition and a weak DA pair transition were observed from the square facet. On the other hand, an emission line at 3.293eV was obtained from the inclined facets. By studying its temperature dependence, we suggest that the 3.293eV emission is due to the free electron to acceptor transition of hexagonal GaN.

We report on the growth of cubic GaN and AlGaN on GaAs (100) substrates by metalorganic vapor phase epitaxy (MOVPE). High optical quality cubic nitrides were obtained by optimizing the growth conditions. X-ray diffraction measurements confirmed the highly cubic nature of these films. Photoluminescence spectra showed dominant excitonic transition for both cubic GaN and AlGaN. Strong stimulated emission was observed from the cleaved edge of optically pumped cubic GaN/AlGaN double hetero (DH) structures.

We have grown cubic AlxGa1−xN (0<x<0.25) films on GaAs (100) substrates by metalorganic vapor phase epitaxy. A strong excitonic transition, as well as a donor–acceptor pair transition and a deep-level emission, was observed in the photoluminescence spectra at 5 K in all the samples. With increasing Al fraction, all the emission lines shift to higher energy, nevertheless, with different shift rates. The temperature-dependent photoluminescence spectra show that the behavior of the donor–acceptor pair transition varied with Al fraction; at higher Al concentrations, the donor–acceptor pair transition tends to transform to a free-electron to acceptor transition and survive even at room temperature. This can also explain the energy shift to higher energy with increasing temperature for this emission line.

We investigated the optical transitions in cubic GaN films grown on GaAs(100) substrates by metalorganic vapor-phase epitaxy. The cubic GaN films show good optical quality. From temperature and excitation intensity dependence, the emission lines at 3.274 and 3.178eV were assigned to the excitonic transition and the donor–acceptor pair transition, respectively. We also suggested an additional acceptor level (EA′≈212meV) to explain the origin of the emission lines at 3.088 and 3.056eV, on the basis of the excitation intensity dependence.

GaN films were grown on 3C-SiC substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) as the N source. The crystal structure was strongly affected by both the growth temperature and the V/III ratio. At 600° C, only hexagonal GaN films with their c-axis perpendicular to the substrate surface were grown. At 800° C, relatively high V/III ratios resulted in the growth of hexagonal GaN with their c-axis oriented in the [111] direction while cubic GaN films were obtained at lower V/III ratios. The origin of [111]-oriented hexagonal GaN is also discussed.

Photoluminescence (PL) measurements were performed on cubic GaN films grown on GaAs(100) substrates by metalorganic vapor phase epitaxy. The cubic GaN films show a high optical quality that enables us to study the PL spectra in detail. From temperature and excitation intensity dependence, the emission lines at 3.274 and at 3.178 eV were assigned to the excitonic transition and the donor–acceptor pair transition, respectively. We also observed two additional emission lines at 3.088 and 3.056 eV. An excitonic emission at 3.216 eV with full width half maximum value as small as 73 meV was observed at 300 K.