Growth and characterization of semi-insulating GaN films grown by MOCVD

High resistivity unintentionally doped GaN films were grown on (0001) sapphire substrates by metalorganic chemical vapor deposition. The surface morphology of the layer was measured by both atomic force microscopy and scanning electron microscopy. The results show that the films have mirror-like surface morphology with root mean square of 0.3 nm. The full width at half maximum of double crystal X-ray diffraction rocking curve for (0002) GaN is about 5.22 arc-min, indicative of high crystal quality. The resistivity of the GaN epilayers at room temperature and at 250 degrees C was measured to be approximate 10(9) and 10(6) Omega(.)cm respectively, by variable temperature Hall measurement. Deep level traps in the GaN epilayers were investigated by thermally stimulated current and resistivity measurements.

Growth of high quality semi-insulating InP single crystal by suppression of compensation defects

Deep level defects in as-grown and annealed SI-InP samples were investigated by thermally stimulated current spectroscopy. Correlations between electrical property, compensation ratio, thermal stability and deep defect concentration in SI-InP were revealed. An optimized crystal growth condition for high quality SI-InP was demonstrated based on the experimental results.

Low threshold current density, low resistance oxide-confined VCSEL fabricated by a dielectric-free approach

We present the fabrication process and experimental results of 850-nm oxide-confined vertical cavity surface emitting lasers (VCSELs) fabricated by using dielectric-free approach. The threshold current of 0.4 mA, which corresponds to the threshold current density of 0.5 kA/cm(2), differential resistance of 76 Omega, and maximum output power of more than 5 mW are achieved for the dielectric-free VCSEL with a square oxide aperture size of 9 mu m at room temperature (RT). L-I-V characteristics of the dielectric-free VCSEL are compared with those of conventional VCSEL with the similar aperture size, which indicates the way to realize low-cost, low-power consumption VCSELs with extremely simple process. Preliminary study of the temperature-dependent L-I characteristics and modulation response of the dielectric-free VCSEL are also presented.

Isolation and Characterization of a Methomyl-Degrading Paracoccus sp mdw-1

Methomyl, an extremely toxic pesticide, is widely used in agriculture. A strain named mdw-1 capable of degrading methomyl rapidly was successfully isolated from activated sludge in this study. It could utilize methomyl as the sole carbon or nitrogen source. The optimal temperature and medium pH for its growth and methomyl biodegradation were 30 degrees C and 7.0, respectively. It was identified as a Paracoccus sp. according to its morphological features, physiological and biochemical characteristics, and phylogenetic analysis based on the sequence of 16S rDNA. Gas chromatography-mass spectrometry (GC-MS) analysis showed that methomyl could be completely transformed to S-methyl-N-hydroxythioacetamidate in 10 h of incubation with the isolate mdw-1.

Rhodococcus qingshengii sp nov., a carbendazim-degrading bacterium

A Gram-positive, aerobic, non-motile, mesophilic strain, djl-6(T), able to degrade carbendazim, was isolated from a carbendazim-contaminated soil sample from Jiangsu province, China. The taxonomic position of this isolate was analysed by using a polyphasic approach. Chemotaxonomic analysis including peptidoglycan type, diagnostic sugar composition, fatty acid profile, menaquinones, polar lipids and mycolic acids showed that the characteristics of strain djl-6(T) were in good agreement with those of the genus Rhodococcus. DNA-DNA hybridization showed that it had low genomic relatedness with Rhodococcus baikonurensis DSM 44587(T) (31.8%), Rhodococcus erythropolis DSM 43066(T) (23.8%) and Rhodococcus globerulus DSM 43954(T) (117.7%), the three type strains to which strain djl-6(T) was most closely related based on 16S rRNA gene sequence analysis (99.78, 99.25 and 98.91% similarity, respectively). Based on the phenotypic properties and DNA-DNA hybridization data, strain djl-6(T) (=CGMCC 1.6580(T) =KCTC 19205(T)) is proposed as the type strain of a novel Rhodococcus species, Rhodococcus qingshengii sp. nov.