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The origin of the background carriers in an undoped InAs/GaSb quantum well (QW) at temperatures between 40K and 300K has been investigated using conventional Hall measurements. It is found that the Hall coefficient changes its sign at around 200 K, indicating that both electrons and holes exist in the quantum well. The two-carrier Hall model is thus adopted to analyze the Hall data, which enables the temperature dependence of the carrier density to be obtained. It is found that considerable numbers of holes exist under low temperature conditions (<40 K) in the InAs/GaSb QW, and the hole density is one to two orders higher than that of the electrons within the experimental temperature range. The origin of these low temperature holes and the temperature-dependent behavior of the carrier density over the entire experimental temperature range are then discussed. [ABSTRACT FROM AUTHOR]

The electron density and temperature dependent in-plane spin-dephasing anisotropy in [111]-grown GaAs quantum well (QW) has been investigated by time-resolved magneto-Kerr rotation technique. Due to the specific symmetry of [111]-grown quantum well, the in-plane Rashba and linear Dresselhaus effective spin-orbit magnetic field is parallel to each other for electron wave vectors in all directions. However, an obvious in-plane spin-dephasing anisotropy comparing [211] with [011] crystalline orientations has been observed and discussed in this work. Our results demonstrate the innegligible spin dephasing channel through inhomogeneous broadening induced by the out-of-plane non-linear Dresselhaus field, which arises naturally from the C3 symmetry of [111]-grown GaAs QW. [ABSTRACT FROM AUTHOR]

The carrier lifetime in an InAs/GaSb quantum well grown by molecular beam epitaxy has been investigated by the time-resolved pump–probe reflectivity (PPR) measurement. It is found that the PPR response shows a sign reversal when tuning excitation energy from 1.033 to 0.954 eV. A model is adopted, in which one takes into account the band gap renormalization and band filling effects, to simulate the temporal evolution of the PPR response. The carrier decay time is then extracted at different excitation energy. The carrier decay time of 98 ps obtained at a close resonant excitation of 0.827 eV is denoted as the carrier lifetime at room temperature. The temperature-dependent PPR is also examined to further investigate the dominant carrier decay mechanism. The short carrier lifetime and its very weak temperature-dependent behavior suggests that the carrier lifetime is mainly determined by the carrier capture process by defect levels in GaSb. [ABSTRACT FROM AUTHOR]

'Jincuilei' is a mutant selected from Lonicera macranthoides Hand.-Mazz. It produces abundant flowers that never open with a chlorogenic acid (CGA) content up to 6.0%. Propagation through rooting or grafting has only a 30% survival rate. This study was undertaken to establish an efficient protocol for rapidly regenerating this mutant. Leaf explants were inoculated on Gamborg's B5 medium supplemented with different concentrations of 6-benzyladenine (BA) and 2,4-dichlorophenozyacetic acid (2,4-D). The optimal combination for callus induction was 4.4 µM BA with 2.26 µM 2,4-D, which resulted in 86.7% of leaf explants producing calluses in 4 weeks. Calluses produced from this optimal medium were cultured on Bs medium containing different concentrations of kinetin (KT) and s-naphthalene acetic acid (NAA). The best formulation for shoot induction was Bs medium containing 0.9 µM KT and 5.4 µM NAA in which 73.4% of cultured calluses produced shoots in 8 weeks, and shoot numbers ranged from three to six per callus piece (1 cm³). Adventitious shoots were cut and rooted in half-strength Murashige and Skoog medium supplemented with 14.8 µ.M 3-indolebutyric acid. Roots initiated 10 d after culture, and rooting percentages ranged from 98% to 100%. Plantlets grown in a container substrate in a shaded greenhouse had over a 95% survival rate. During the last 6 years, over four million plantlets were regenerated using this established procedure, and there was no somaclonal variation. Fresh and dry weights of 1000 flowers, CGA contents, and dry flower yields of the regenerated plants were not significantly different from those of the stock 'Jincuilei' propagated by cutting, indicating that plants regenerated from this established procedure were stable. This established in vitro culture method has led to rapid commercial production of this medicinal plant on more than 1500 ha of production field. [ABSTRACT FROM AUTHOR]