Material utilisation when depositing CdTe layers by inline AP-MOCVD

The CdxZn(1-x)S films have been deposited by low cost atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD) technique and the resulting morphological properties were successfully evaluated for solar cell applications. All morphological properties presented here were investigated by Field-Emission Scanning Microscopy (FESEM) and Energy Dispersive X-Ray (EDX) spectroscopy. It has been observed that the film thickness and grain size have been greatly influenced by the molar ratio of cadmium and zinc, deposition temperature and time. The average grain size of Cd0.5Zn0.5S films (98.16 nm thick) was obtained with deposition temperature and time of 440°C and 2.5 minutes, respectively.

Improved output power of GaN-based ultraviolet light-emitting diodes with sputtered AlN nucleation layer

Application of ZnO Nanorods Based Whispering Gallery Mode Resonator in Optical Immunosensors

This report describes research to demonstrate (1) thin film cadmium telluride solar cells with a quantum efficiency of 75% or higher at 0. 44 {mu}m and a photovoltaic efficiency of 11.5% or greater, and (2) thin film zinc telluride and mercury zinc telluride solar cells with a transparency to sub-band-gap radiation of 65% and a photovoltaic conversion efficiency of 5% and 8%, respectively. Work was directed at (1) depositing transparent conducting semiconductor films by solution growth and metal-organic chemical vapor deposition (MOCVD) technique, (2) depositing CdTe films by close-spaced sublimation (CSS) and MOCVD techniques, (3) preparing and evaluating thin film CdTe solar cells, and (4) preparing and characterizing thin film ZnTe, CD{sub 1-x}Zn{sub 1-x}Te, and Hg{sub 1-x}Zn{sub x}Te solar cells. The deposition of CdS films from aqueous solutions was investigated in detail, and their crystallographic, optical, and electrical properties were characterized. CdTe films were deposited from DMCd and DIPTe at 400{degrees}C using TEGa and AsH{sub 3} as dopants. CdTe films deposited by CSS had significantly better microstructures than those deposited by MOCVD. Deep energy states in CdTe films deposited by CSS and MOCVD were investigated. Thin films of ZnTe, Cd{sub 1- x}Zn{sub x}Te, and Hg{sub 1-x}Zn{sub x}Te were deposited by MOCVD, and their crystallographic, optical, and electrical properties were characterized. 67 refs.

In this letter we demonstrate that the anomalously low (002) x-ray rocking curve widths for epitaxial hexagonal GaN films on (001) sapphire are a result of a specific threading dislocation (TD) geometry. Epitaxial GaN films were grown on c-plane sapphire by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) in a horizontal flow reactor. Films were grown with (002) rocking curves (ω-scans) widths as low as 40 arcsec and threading dislocation densities of ∼2×1010 cm−2. The threading dislocations in this film lie parallel to the [001] direction and within the limit of imaging statistics, all are pure edge with Burgers vectors parallel to the film/substrate interface. These TDs will not distort the (002) planes. However, distortion of asymmetric planes, such as (102), is predicted and confirmed in (102) rocking curve widths of 740 arcsec. These results are compared with films with (002) rocking curves of ∼270 arcsec and threading dislocation densities of ∼7×108 cm−2.

Roll-over behavior in current-voltage curve introduced by an energy barrier at the front contact in thin film CdTe solar cell

A novel method of the selective epitaxy of InP was developed by employing a two-step growth in atmospheric pressure metalorganic chemical vapor deposition. By this method, selective epitaxy, without ridge and/or lateral growth, and with uniform deposition of the polycrystalline layer on the SiO2 mask, could be achieved. First, a thin uniform InP polycrystalline layer was deposited on a SiO2/InP substrate and a stripe pattern was formed by photolithography, and then selective epitaxial growth was performed. Selective epitaxial layers thus obtained were found to have a photoluminescence half width of ∼40 meV at room temperature, which was comparable to the one reported by other workers in homoepitaxial metalorganic chemical vapor deposition growth of InP. The resistivity of the polycrystalline layer was ∼700 Ω cm at room temperature, which was four orders of magnitude larger than that of the selective epitaxial layer. Therefore, electrical isolation may be sufficient for fabrication of InP planar devices.

We fabricated inorganic-organic hybrid heterojunction between indium phosphide (InP) and pentacene for photodetector application. InP layer was grown on n-Si substrate by atmospheric pressure metal organic chemical vapour deposition (MOCVD) technique. Morphological properties of InP and pentacene thin film were characterized by atomic force microscopy (AFM). Current-voltage characteristics were investigated in dark and under illumination condition at room temperature. During illumination, different wavelengths of visible and infrared light source were employed to perform the electrical measurement. Enhancement of photocurrent was observed with decreasing in wavelength of incident photo radiation. Ideality factor was found to be 1.92. High rectification ratio of 225 was found at ± 3 V in presence of infrared light source. This study provides new insights of inorganic-organic hybrid heterojunction for broadband photoresponse in visible to near infrared (IR) region under low reverse bias condition.

In x Ga1−x As (0·06≤x≤0·35) epilayers were grown on GaAs substrates by atmospheric pressure metal organic chemical vapour deposition technique. Surface morphology and lattice mismatch in the InGaAs/GaAs films of different compositions were studied. Cross-hatched patterns were observed on the surface of the epilayers for bulk alloy composition up tox≈0·25. Forx>0·3, a rough textured surface morphology was observed.

Gallium-doped ZnO films were grown on p-Si(111) substrates by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using diethylzinc and water as reactant gases and triethyl gallium (TEG) as a n-type dopant gas. The structural, electrical, and optical properties of ZnO:Ga films obtained by varying the flow rate of TEG from 0.56to3.35μmol∕min were examined. X-ray diffraction patterns and scanning electron microscopy images indicated that Ga doping plays a role in forming microstructures in ZnO films. A flat surface with a predominant orientation (101) was obtained for the ZnO:Ga film fabricated at a flow rate of TEG=2.79μmol∕min. This film also revealed a lowest resistivity of 4.54×10−4Ωcm, as measured using the van der Pauw method. Moreover, low temperature photoluminescence (PL) emission recorded at 12K demonstrated the Burstein Moss shift of PL line from 3.365to3.403eV and a line broadening from 100to165meV as the TEG flow rate varied from 0.56to2.79μmol∕min. This blueshift behavior of PL spectra from ZnO:Ga films features the degeneracy of semiconductor, which helps to recognize the enhancing of transparency and conductivity of ZnO films fabricated by AP-MOCVD using Ga-doping technique.

Preparation and characterization of MgTiO 3 thin films by atmospheric pressure metalorganic chemical vapor deposition

Properties of alumina films prepared by atmospheric pressure metal-organic chemical vapour deposition

We report on the investigation of the effect of growth temperature on point defect density of unintentionally doped GaN grown by atmospheric pressure metalorganic chemical vapor deposition and hydride vapor phase epitaxy. A correlation between photoluminescence (PL) spectra and the concentration of donors and acceptors in unintentionally doped GaN is presented. The effects of oxygen and native acceptors on the electrical and optical properties of GaN epitaxial layers are discussed and a classification of PL data is presented. On this basis we show that oxygen creates a shallow donor in GaN with an activation energy of about 23.5±1 meV. We determine that the concentration of native acceptors in GaN increases with an increase in growth temperature. These native acceptors, probably gallium antisites (GaN) and/or gallium vacancies (VGa), are nonradiative defects. We show that a second donor level in GaN has an activation energy of about 52.5±2.5 meV and produces a PL peak with an energy of about 3.45 eV at low temperatures. From Hall investigations we show that a third donor in GaN has an activation energy of 110±10 meV.

We have investigated the properties of center and edge δ-doped GaAs-AlGaAs quantum wells grown by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) by means of capacitance voltage (C-V) profiling and temperature-dependent photoluminescence (PL) measurements. For the center δ-doped quantum well, a narrow C-V profile and the Fermi-edge singularity in PL have been confirmed. In contrast, for edge δ-doped quantum wells, a double-peaked C-V profile and a sharp luminescence enhancement near the Fermi level which is not due to the Fermi-edge singularity, have been observed. The results are explained by a simple model based on the asymmetrical potential well induced by the band bending due to the δ-doping at one side of the heterointerfaces.

Structural, electrical, and optical properties of CoxNi1-xO films grown by metalorganic chemical vapor deposition