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Notes: Detailed measurements of polarization-dependent gain-current characteristics have been carried out on (111)- and (100)-oriented GaAs/AlGaAs single-quantum-well lasers by using Hakki and Paoli's method. Polarization-dependent gain-current characteristics have been found to strongly depend on the well width and the quantization direction. The saturation of gain with the injection current and the width of the gain spectrum depends on the well width, and they are also affected by the transition between the higher-order subbands. Experimental results of polarization-dependent spontaneous emission are also presented. The simple selection rule and the effective-mass theories do not quantitatively account for the experimental results.

Notes: High-purity Al0.3Ga0.7As is grown by molecular beam epitaxy at a high substrate temperature using a superlattice buffer layer in order to trap residual impurities. The unintentionally doped layer is p type with p 〈 5×1014 cm−3. Photoluminescence spectra at 10 K showed the strong bound-exciton emission to be 3.8 meV wide and extremely weak emission due to residual C and Si. Photoluminescence spectra of successively grown single-quantum wells with different widths demonstrate that residual C and Si are mainly trapped at the interface of the first-grown well.

Notes: The energy-band structure of (AlAs) (GaAs) short-period superlattices (SLs) has been investigated by using photoluminescence and photoluminescence excitation spectroscopy. In the indirect transition region, both direct and indirect transitions are simultaneously observed and the band structure is elucidated. Indirect-direct crossover occurs in the region of 15–18 A(ring) GaAs thickness for SLs with 10-A(ring) AlAs thickness.

Notes: Using time-resolved photoluminescence, we examined the carrier-recombination process in strained AlGaInP/GaInP double heterostructures grown by metal-organic vapor phase epitaxy. We found that interfacial recombination dominates the process at room temperature, and that the interfacial recombination is enhanced by tensile strain and reduced by compressive strain.

Notes: We fabricated a GaInP/AlGaInP visible laser with a real-index guide structure by one-step metalorganic vapor phase epitaxy using simultaneous impurity doping. We achieved an effective self-aligned current-confinement structure in the AlGaInP cladding layer and a threshold current of only 18 mA. The laser had stable transverse-mode oscillation with a beam astigmatism less than 1 μm.

Notes: The optical gains in AlGaInP/GaInP strained quantum wells using valence band structures by the second-order k⋅p method, with and without spin-orbit split-off (SO) band effect have been calculated. It was easy to overestimate the optical gain without considering the SO-band effect, because a small spin-orbit splitting energy for GaInP makes higher nonparabolicity of the valence bands. The SO-band effect is particularly significant under tensile strain, since the SO band makes the effective mass very large due to the large interaction between the SO and light hole bands. © 1995 American Institute of Physics.

Notes: We have investigated the role of hydrogen in hydrogenated microcrystalline silicon (μc-Si:H) formation using hydrogen plasma treatments, in particular examining the possibility of subsurface reaction due to permeating hydrogen atoms, which leads to the crystallization of hydrogenated amorphous silicon (a-Si:H). It is demonstrated that the hydrogen plasma treatment of a-Si:H film on the anode using a cathode covered by a-Si:H film, which is inevitably coated during the deposition period, gives rise to the deposition of μc-Si:H over the a-Si:H layer, i.e., chemical transport takes place. It is also found that the pure hydrogen plasma treatment using a clean cathode induces only etching of the a-Si:H layer. These results imply that the present hydrogen plasma condition does not cause crystallization of a-Si:H but only etching, and that careful experimentation is required to determine the real subsurface reaction due to atomic hydrogen. © 1997 American Institute of Physics.

Notes: Low-temperature processing for high-performance solar cells based on hydrogenated microcrystalline silicon (μc-Si:H) has been developed using a conventional rf plasma-enhanced chemical vapor deposition (PECVD) technique at an excitation frequency of 13.56 MHz under a high deposition pressure condition. Among pin type solar cells, it is found that deposition temperature of i-layer at 140 °C is effective particularly for improving open circuit voltage (Voc), surprisingly without deteriorating short circuit current or fill factor. Carrier density of undoped μc-Si abruptly decreases for deposition temperatures lower than 180 °C, and the improvement of Voc is ascribed to a decrease of shunt leakage current arising from the oxygen-related donors. This implies that oxygen-related donors can be passivated at low deposition temperatures and that hydrogen plays an important role for the passivation. We propose a simple model for the hydrogen passivation of oxygen related donors. We apply this passivation technique to solar cells, and consequently a conversion efficiency of 8.9% (Voc=0.51 V, Jsc=25 mA/cm−1, FF=0.70) has been obtained in spite of an oxygen concentration of 2×1019 cm−3 in combination with device optimization such as a p-layer. Effect of deposition temperature of i-layer upon other solar cell parameter, short circuit current, and fill factor is also discussed. © 2001 American Institute of Physics.

Notes: Background Transforming growth factor-β1 (TGF-β1) is generally considered to play an important role in the pathogenesis of chronic inflammation and fibrosis.Objective and methods This study was designed to determine mechanisms of reduced responsiveness of guinea-pig tracheal smooth muscle to β-adrenoceptor agonists by TGF-β1, using isometric tension records and tissue cAMP measurement. Moreover, we examined the involvement of the signal transduction processes of TGF-β superfamily in the desensitization of β-adrenoceptors.Results After exposure to 0.2–2000 pm TGF-β1 for 4–8 h, the inhibitory effects of 1 µm isoprenaline (ISO) and 10 µm forskolin on 1 µm MCh-induced contraction were markedly reduced in a concentration-dependent fashion. The desensitization by TGF-β1 was greater against ISO than for forskolin. The values of EC75 for the curves for ISO after exposure to the normal bathing solution and TGF-β1 were 0.039 ± 0.02 and 0.38 ± 0.28 µm, respectively. The values of EC50 for the curves for forskolin under these conditions were 0.50 ± 0.12 and 0.89 ± 0.21 µm, respectively. On the other hand, the inhibitory effects of phosphodiesterase inhibitors such as theophylline and rolipram were not attenuated after exposure to TGF-β1. Concentration–inhibition curve for ISO was shifted to the right after exposure to 2000 pm TGF-β1 for 8 h more than that curve for forskolin. In contrast, the curve for theophylline was not shifted to the right by TGF-β1. When the tissues were incubated with TGF-β1 in the presence of IFN-γ, an intracellular antagonist of TGF-β signalling, IFN-γ inhibited the reduced response to ISO and forskolin after exposure to TGF-β1 in a concentration-dependent fashion. After exposure to TGF-β1, the effects of cAMP accumulation of ISO was significantly reduced, however, neither forskolin-nor theophylline-induced cAMP accumulation was affected. IFN-γ had no significant effect on cAMP accumulation either to ISO or forskolin.Conclusions Impairment of the β-adrenoceptors/adenylyl cyclase pathway are involved in heterologous desensitization of β-adrenoceptors induced by TGF-β1 in airway smooth muscle. IFN-γ functionally suppresses this phenomenon via cAMP-independent processes. Phosphodiesterase is still intact under this condition.