Vol. 33 No. 1 (2001)

. We have studied the effect of hydrogen plasma on GaN film, grown by plasma-assisted metalorganic chemical vapor deposition (MOCVD). GaN films grown on a sapphire (0001) without the buffer layer have a polycrystalline structure. While films grown using the buffer layer tends to have a single crystal orientation. We have tried to increase the growth rate by varying the TMGa:N ratio. We found that the growth rate of the films were 450 nm/h with TMGa:N ratio of 1:600. However the films show a polycrystalline structure. Using hydrogen plasma during the growth, we have shown by XRD analysis that…

. GaSb and Al GaSb are narrow gap semiconductors, is of current interest, for its optoelectronic application in the near and medium infra-red region. The large ratio of the ionization coefficient of hole and electrons is key factor for high speed and low noise in APD. In this paper we report the frowth of GaSb and AlGaSb in a home made vertical MOCVD reactor using trymethylgalium (TMGa), trymethylalumunium (TMAl) and tridismethylaminiantimonat (TDMASb) as metalorganic sources. In the reactor we used a flow guide to obtain uniform layers. The effect of growth temperature and the V/III ratio on…

. Quantum Dots is a nano structured materials, which is an interesting object for fundamental study as well as for applications. Quantum Dots has been used for optoelectronic devices, such as fast detectors and for lasers. In this paper we report preliminary results of the preparation of quantum dots of GaSb in our laboratory. These dots are prepared by self-organized growth by MOCVD, using Trymethylgalium and Tridismethylaminoantimonat as metal organic sources and using GaAs as substrate. The results are studied by Scanning Electron Microscope. We propose further characterization of these…

. The application of double barrier (DB) structure in p-i-n amorphous silicon (a-Si) device was studied. The theoretical study was done to obtain device parameters such as tunneling probability and current density. The tunneling probability was calculated by employing the Schroedinger equation, WKB approximation and Green function. Width of potential well, width and height of barrier were varied to obtain the highest tunneling probability value. The current density was contributed by diffusion, and tunneling current densities. It was found that current density had a peak of 3950 A/m2 at 0.56…

. Effect of B-doping B2H6 on the crystal structural and optical properties of zinc oxide (ZnO) thin films has been studied. The crystal orientation of these films were evaluated by X-ray diffraction. It was found that the (110) reflection peak was dominant for all the film and became less pronounced as B2H6 flow rate was increased. The grain size of thin film decreased as B2H6 flow rate was increased. The transmittance in the ultraviolet wavelengths region shifted to higher energy as the B2H6 flow rate was increased. I t was also found that refractive index of ZnO thin films increased as the…

The annealing treatment of ZnO thin film at various temperatures was performed. The effect of this treatment on the optical properties of ZnO thin film were investigated in order to apply this film to optoelectronic devices. The optical transmittance spectra were measured and it was found that the transmittance in UV-VIS region decreased with annealing temperature. The loss of light is mainly due to the increase of carrier density, resulting from increased oxygen vacancies during the annealing process at 300°C. It was also found that the absorption edge shifted to lower energy when the film…

. Highly crystalline thin films of photorefractive Disperse Red 1 (DR 1) molecule have been fabricated on clean substrate of ITO (indium tin oxide) glass by means of physical vapor deposition at various substrate temperatures. In addition to molecular orientation and organization revealed by their XRD and FTIR spectral characteristic and the enhancement of those effects by substrate temperature, further analysis of FTIR spectrum around nitrobenzene absorption band indicates the formation of strong hydrogen bond resulting in a head-tail stacking of the molecules. The deposited films also show…