M. D. Kim

Hydrogenation and annealing effects in p-type ZnSe thin films grown on GaAs (100) substrates

Photoluminescence (PL) and Raman scattering measurements have been carried out to investigate the hydrogenation and annealing effects in p-type ZnSe epilayers grown on n-type GaAs (100) substrates by molecular beam epitaxy. After hydrogenation, the PL spectra showed that the deep acceptor-bound exciton peak disappeared and that the peak position of the donor–acceptor pair peak shifted to a higher energy. When the hydrogenated ZnSe/GaAs heterostructure was annealed at 300 °, a bound exciton due to neutral acceptors appeared. The Raman intensity of the plasma longitudinal optical-phonon-coupling mode increased after hydrogenation. These results indicate that the crystallinity of the p-type ZnSe epilayers grown on n-type GaAs substrates is improved by hydrogenation and that hydrogenated and annealed ZnSe films grown on GaAs substrates hold promise for potential application as buffer layers for the growth of Zn1−xMgxSySe1−y active layers.

Hydrogenation and annealing effects on the deep levels and acceptor neutralization in p-CdTe

Abstract Photo-induced-current transient spectroscopy and capacitance–voltage measurements on nominally undoped p-CdTe single crystals grown by a Bridgman method have been carried out to investigate the hydrogenation and the annealing effects on the deep levels and on acceptor neutralization. The five hole-traps of the as-grown p-CdTe and their activation energies were E v +0.21 (H 1 ), E v +0.39 (H 2 ), E v +0.43 (H 3 ), E v +0.65 eV (H 4 ), and E v +0.75 (H 5 ). After the p-CdTe was hydrogenated and annealed, H 4 and H 5 related to Cd vacancies disappeared, and the intensity of H 3 related to the native defects decreased by a factor of 2. H 4 and H 5 traps were passivated by the hydrogen atoms. The H 3 defect level is considered to be due to complexes of Cd vacancies and impurities, and the H 2 signal is associated with complexes of shallow impurities. The results of the PICTS measurements showed that hydrogen atoms easily neutralize the Cd vacancies and that the hydrogen atoms are easily separated from the impurities by the thermal energy. These results indicate that the electrical properties of the undoped p-CdTe single crystals are improved by hydrogenation and annealing and that hydrogenated and annealed CdTe crystals hold promise as useful substrates for the growth of Hg x Cd 1 x Te.

Hydrogenation and annealing behaviors of deep levels in strained CdTe(111)/GaAs(100) heterostructures

Photo-induced-current transient spectroscopy measurements on CdTe/GaAs strained heterostructures grown by molecular beam epitaxy were carried out to investigate the hydrogenation and the annealing behaviors of the deep levels due to the crystal defects. The six hole-traps of the as-grown CdTe epilayer were observed. As the growth temperature and the rapid thermal annealing (RTA) temperature increased, the intensities of the H5 and the H6 peaks due to the crystal defects decreased, and that of the peak related to the shallow impurities increased. After annealing, the H5 and the H6 deep levels did not disappear in CdTe/GaAs heterostructures. These results indicate that the H5 and the H6 deep levels are related to the crystal defects due to the lattice mismatch. While the H6 signal was remarkably affected by the growth temperature of the CdTe epilayer, it was independent of the thickness of the CdTe. These results indicate that the crystallinity of a CdTe epilayer grown on GaAs(100) is improved by RTA, and t...

Effect of the Climatic Condition on the Growth Characteristic of Domestic Corn Hybrids in Alpine Region

The aim of the present study was to investigate the relationship between climates, growth characteristic and yield of silage corn at Hanwoo Experiment Station, National Institute of Animal Science, Daegwallyeong in Gangwon Province located at altitude of 760 m, from 2009 to 2010. The mean minimum temperature was from seeding to harvest in 2009, in 2010, the mean maximum temperature was , , respectively. The mean temperature was in 2009 and in 2010, respectively. Duration of sunshine was 711.3 hours in 2009 and 663.8 hours in 2010, and precipitation was 893.8 mm in 2009 and 752.1 mm in 2010, respectively. In 2009, for all Kwangpyeongok, Gangdaok, Cheonganok, Cheongsaok, Pyeonganok, the early growth was good with 1.2, while in 2010 the growth for Pyeonganok was good with 1.3 comparing to others, which showed worse growth than in the previous year with 2.4~3.0. There was significant difference in the ear height between 2009 and 2010, showing mean value of 85.8 cm and 105 cm for all the species in 2009 and in 2010, respectively (p

Effects of Fiber Sources on Ruminal pH, Buffering Capacity and Digestibility in Sheep

This study was conducted to study the effect of fiber sources on ruminal pH and buffering capacity and whole digestive tract digestibility with five ruminally fistulated sheep. Evaluated fiber sources were alfalfa hay cube (AHC), corn cob (CC), com silage (CS), cotton seed hull (CSH), peanut hull (PHL), rice straw (RS), and sugarcane bagasse (SCB). Sheep were fed consecutively a diet containing each tested fiber source with a corn-based concentrate diets during each experimental period. Ruminal pH showed no difference among fiber sources except the significantly lower pH at 8h (p

Effect of hydrogenation on the electrical and optical properties of p-type Zn1−xMgxSySe1−y epitaxial layers grown on GaAs (100) substrates

Abstract Capacitance–voltage ( C – V ) and photoluminescence (PL) measurements have been carried out to investigate the hydrogenation effects on the electrical and the optical properties in p-type Zn 0.92 Mg 0.08 S 0.13 Se 0.87 epilayers grown on n-type GaAs (100) substrates by molecular beam epitaxy. The results of the high-resolution transmission electron microscopy showed that the Zn 0.92 Mg 0.08 S 0.13 Se 0.87 /GaAs heterostructure had a high-quality heterointerface with sharp interface. After hydrogenation, the acceptor–carrier concentration of the p-type Zn 0.92 Mg 0.08 S 0.13 Se 0.87 decreased due to acceptor neutralization resulting from complexes forming between the hydrogen atoms and the Zn or Se vacancies. After hydrogenation, the PL spectrum showed new donor-bound exciton and free electron-to-acceptor peaks, and the peak position of the donor–acceptor pair peak shifted to higher energy due to hydrogenation neutralization of the acceptor impurities. These results indicate that the crystallinity of the p-type Zn 0.92 Mg 0.08 S 0.13 Se 0.87 epilayers grown on n-type GaAs substrates is improved by hydrogenation and that hydrogenated Zn0 .92 Mg 0.08 S 0.13 Se 0.87 films grown on GaAs substrates hold promise for potential applications as cladding layers in optoelectronic devices operating in the blue–green spectral region.

Effects of Crude Protein Levels on Nitrogen Balance in Adult Jindo Dog

This study was conducted to determine the protein requirement level in adult Jindo dog (Korea Jindo Dog) through nitrogen balance experiments. 12 female dogs aged 36~38 weeks old (for early stage) or aged 45~49 weeks old (for late stage) were fed one of 3 diets containing 17, 19 and 21% of crude protein. Body weight of dogs were measured during the 12 days of feeding trial, and feces and urine were collected last 3 days of the trial period. In early stage of Jindo dog, average daily gain of dogs fed experimental diets containing 17, 19 and 21% of crude protein were 38.33, 16.25 and 12.71g/d, respectively. There was a significant differences between 17 and 21% of crude protein treatments (p<0.05) and calculated retained nitrogen were 0.29, 0.04 and 0.03g/kgBW .75 /d, respectively. In late stage of Jindo dog, average daily gain of dogs fed experimental diets containing 17, 19 and 21% of crude protein were 34.05, 28.71 and -28.28g/d, and calculated retained nitrogen were 0.33, 0.06 and 0.09g/kgBW .75 /d, respectively, and were significantly higher (p<0.05) in dogs fed 21% of crude protein diet than those of other dogs. In early stage and late stage of adult Jindo dog, a calculated linear regression equation for nitrogen intake (x) and nitrogen retention (y) were y = 0.7484x 1.18 (R 2 = 0.9923) and y = 0.88231x 1.0894 (R 2 = 0.9982) and the requirement of crude protein were estimated as 9.85g/kg BW .75 /d and 7.72g/kg BW .75 /d from above equation.

Hydrogenation and annealing effects on electronic subbands in modulation-doped Al0.25Ga0.75As/In0.18Ga0.82As/GaAs strained single quantum wells

Abstract Photoluminescence (PL) measurements have been carried out to investigate the hydrogenation and annealing effects on the excitonic transitions in modulation-doped Al 0.25 Ga 0.75 As/In 0.18 Ga 0.82 As/GaAs strained quantum wells. After hydrogenation, the PL spectra showed that the excitonic transition energy from the ground electronic subband to the ground heavy-hole subband ( E 0 −HH 1 ) shifted to a higher energy. When the hydrogenated Al 0.25 Ga 0.75 As/In 0.18 Ga 0.82 As/GaAs quantum wells was annealed, the ( E 0 −HH 1 ) peak shifted to a lower energy. The electronic subband energies, the energy wave functions, and the Fermi energies in the as-grown modulation-doped Al 0.25 Ga 0.75 As/In 0.18 Ga 0.82 As/GaAs quantum wells were calculated by a self-consistent method taking into account exchange-correlation effects together with the strain and nonparabolicity effects. These results indicate that the energy levels of the electronic subbands in the In 0.18 Ga 0.82 As quantum well are dramatically affected by the hydrogenation and the annealing and that the shifts of their energy levels due to the hydrogenation and the annealing can help improve understanding of the promising applications of modulation-doped Al 0.25 Ga 0.75 As/In 0.18 Ga 0.82 As/GaAs strained quantum wells in optoelectronic devices.

Structural properties of lattice matched Zn0.92Mg0.08S0.12Se0.88/GaAs heterostructures

Abstract A nearly lattice-matched Zn 0.92 Mg 0.08 S 0.12 Se 0.88 epilayer was grown on a GaAs (100) substrate by molecular beam epitaxy. The compositional profile of the Zn 0.92 Mg 0.08 S 0.12 Se 0.88 layers were investigated by Auger electron spectroscopy. Transmission electron microscopy measurements were performed to investigate the crystallinity of the epitaxial layer and the interface. These results indicate that Zn 0.92 Mg 0.08 S 0.12 Se 0.88 epitaxial films grown on GaAs substrates at 250°C have good interface structure and no serious interdiffusion problems and that the Zn 0.92 Mg 0.08 S 0.12 Se 0.88 layers hold promise for applications as cladding layers for laser diodes and related optoelectronic devices operating in the blue spectral range.

Hydrogenation effect of InGaP grown on GaAs by molecular beam epitaxy

Hydrogenation effects on the electrical properties of n-type and undoped InGaP epilayers lattice matched to GaAs were investigated. It was found that hydrogenation under proper conditions can result in a Au/n-InGaP Schottky diode with good rectifying characteristics as well as effective defect passivation. These improvement were thought to result from the atomic hydrogen diffusion into InGaP which neutralized Si donors and passivated recombination centers near the surface.