摘要:

We have studied the effects of metalorganic chemical vapor deposition (MOCVD) growth conditions on the properties of GaAs solar cells grown upon Ge substrates, and in particular the GaAs/Ge interface. The interface properties were found to strongly depend on growth conditions. By small changes in the growth temperature, the GaAs/Ge interface was altered from active to passive. Only a narrow temperature window (600–630 °C) for the initial GaAs layer growth gave the passive‐Ge junction together with good surface morphology. Accordingly, a high efficiency (19%, AM0) GaAs solar cell was grown by atmospheric pressure MOCVD on a Ge substrate without any junction in the Ge.

ISSN:0003-6951    

DOI:10.1063/1.104899

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Pseudomorphic (In,Ga)As layers are used in GaAs‐based semiconductor‐insulator‐ semiconductor (SIS) structures to shift the threshold voltage from the natural, near‐zero value. The threshold voltage is shifted positively for (In,Ga)As gate layers, and negatively for (In,Ga)As channel layers, by the (In,Ga)As/GaAs conduction‐band offset. The thermionic and field emission barrier heights agree with shifts obtained in capacitance‐voltage characteristics. The structures withstand implant activation anneals, establishing a simple technology to create either enhancement or depletion‐mode devices.

ISSN:0003-6951    

DOI:10.1063/1.104900

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Three‐dimensional boron impurity concentration profiles in silicon substrates have been measured with 10 nm resolution by scanning tunneling microscopy (STM) on chemically etched cleaved silicon surfaces using an impurity sensitive HF‐HNO3‐H2O solution. Comparisons to depth profiles obtained with secondary‐ion mass spectroscopy and spreading resistance methods reveal that our proposed method measures activated boron impurity concentration rather than total boron concentration. Three‐dimensional impurity profiling is demonstrated with a metal‐oxide‐silicon structure, and the lateral junction depth in the test structure is found to be 70% of the junction depth.

ISSN:0003-6951    

DOI:10.1063/1.104901

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Oscillations have been obtained at frequencies from 100 to 712 GHz in InAs/AlSb double‐barrier resonant‐tunneling diodes at room temperature. The measured power density at 360 GHz was 90 W cm−2, which is 50 times that generated by GaAs/AlAs diodes at essentially the same frequency. The oscillation at 712 GHz represents the highest frequency reported to date from a solid‐state electronic oscillator at room temperature.

ISSN:0003-6951    

DOI:10.1063/1.104902

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Epitaxial MgO thin films were grown on Si(001) by pulsed laser deposition. In spite of a large (−22.5%) lattice mismatch, epitaxy occurs with alignment of all crystallographic axes. Epitaxial quality and deposition rate are both sensitive to temperature and oxygen pressure. We believe this is the first demonstration of epitaxial MgO on Si. We employ MgO intermediate layers for superconducting epitaxial YBa2Cu3O7−&dgr;/BaTiO3thin films on Si with a critical current density of 6.7×105A/cm2at 77 K.

ISSN:0003-6951    

DOI:10.1063/1.104903

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The thin Bi(Pb)‐Sr‐Ca‐Cu‐O film composed of the highTcphase has been successfully made by the thermal decomposition method using an organic acid salt, which is spread on the MgO(100) substrate by the spin‐coat method. A preannealing process before a final annealing is added to the usual film preparation in order to prevent the metallic compounds in the salt from diverging to the atmosphere. The film obtained here has a flatter and smoother surface, and a higher zero‐resistivity temperatureTc0(=107.0 K) than those of the films without the preannealing process. However, the homogeneity of the film seems to be slightly insufficient as the onset critical temperature of the real part of a complex susceptibility is about 3 K larger thanTc0.

ISSN:0003-6951    

DOI:10.1063/1.104904

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

YBa2Cu3O7−xsuperconducting thin films prepared by chemical vapor deposition which exhibit high transition temperatures (Tc∼90 K) and high critical current densities (Jc≳106A/cm2at 77.7 K and 0 T) generally have copper‐rich precipitates on the surface. We have studied both near‐stoichiometric and nonstoichiometric highlyc‐axis oriented thin films formed by plasma‐enhanced metalorganic chemical vapor deposition. We show that the reduction in transport properties (TcandJc) observed in stoichiometric films with smooth morphologies may result from a dramatic reduction of the oxygen diffusion rate in these thin films as compared to nonstoichiometric films. The significant enhancement of the transport properties of these films was achieved by further oxygen anneals at 480 °C.

ISSN:0003-6951    

DOI:10.1063/1.104905

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the first real time,insitusynchrotron x‐ray studies of Y‐Ba‐Cu‐O thin‐film growth on (100) SrTiO3using a miniature, faced‐magnetron sputtering system. A combination of the substrate temperature and the deposition rate determines whether the film grows along thea,c, or multiple axes.

ISSN:0003-6951    

DOI:10.1063/1.104906

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Sputtered Fe/Mo superlattices grown on sapphire exhibit an oscillatory magnetic coupling as a function of Mo thickness. Ferromagnetic Fe layers 25 A˚ thick couple across the nonmagnetic Mo layers ferro‐ or antiferromagnetically with a period of ∼11 A˚ Mo. Ferromagnetically aligned films show the anticipated trend in longitudinal Kerr‐rotation values based on calculation, while the antiferromagnetically coupled films in zero field yield only weak Kerr signals due to their characteristically ‘‘pinched’’ hysteresis loops. The films are well ordered and exhibit up to seven low‐angle, x‐ray diffraction peaks, but have negative magnetoresistive anomalies that are only ≲2% at 4.2 K.

ISSN:0003-6951    

DOI:10.1063/1.104907

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on the production of atomic hydrogen subsequent to the 193 nm photolysis of triethylarsenic (TEAs) using an excimer laser. The H atoms are probed via two‐photon (121.6+364.7 nm) ionization, and the resulting H atom Doppler profile at Lyman‐&agr; is presented. Photolysis power dependence studies demonstrate that substantial H atom formation occurs at relatively low laser powers. However, the H atom signal actually begins to diminish as the photolysis laser power is increased beyond ∼70 MW/cm2. Correlations with time‐of‐fight mass spectral data suggest that ion channels are being accessed. The possible mechanisms for TEAs excitation that lead to H atom formation/depletion are presented, and the implications of these observations on controlling carbon incorporation in the laser‐enhanced growth of films of GaAs, AlGaAs, etc. are discussed.

ISSN:0003-6951    

DOI:10.1063/1.104908

出版商:AIP    

年代:1991

数据来源: AIP