摘要:

We report on the first observation of different nitrogen pair complexes in GaAs. These complexes, which have been searched for since the ’60s, are studied under the application of hydrostatic pressure. By carefully tuning the pressure, we make one after the other of the NNipairs (1≤i≤10) appear in the band gap of GaAs and then become the major exciton recombination channel. We compare our results for nitrogen states in GaAs with the classical case of NNiexcitons in GaP.

ISSN:0003-6951    

DOI:10.1063/1.102495

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Hydrogen passivation of deep traps in diamond is demonstrated. Current‐voltage (I‐V) characteristics of polycrystalline thin film and bulk diamond were studied before and after hydrogenation. On hydrogenation, all the samples showed several orders of magnitude increase in conductivity. Hydrogenation was carried out under controlled conditions to study the changes in theI‐Vcharacteristics of the samples. The concentration of uncompensated traps was varied systematically by hydrogenation. The concentration of electrically active hydrogen was determined from theI‐Vdata. It is shown that hydrogenation is an alternative to deep‐level transient spectroscopy, suitable for characterization of traps in a wide‐band‐gap material like diamond.

ISSN:0003-6951    

DOI:10.1063/1.102496

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Transport of the acceptor‐passivating hydrogen species inp‐type GaAs has been observed in reverse bias annealed Al Schottky diode samples. The motion of the positively charged hydrogen across the depletion region of these diodes is confirmed both by changes in the electrically active acceptor profiles with time, and by direct measurement of the migration using secondary‐ion mass spectrometry on deuterated samples. Acceptor passivation is unstable under minority‐carrier injection by illumination at 25 °C. Hydrogen injection intop‐type GaAs during boiling in water or etching in H2SO4:H2O2:H2O has also been demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.102497

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Heterostructure bipolar transistors are used to experimentally determine band offsets in lattice‐matched In0.53Ga0.47As devices. Valence‐band offsets of &Dgr;EV=0.24 eV for Al0.48In0.52As/In0.53Ga0.47As and &Dgr;EV=0.34 eV for InP/In0.53Ga0.47As are measured. Because of band filling in the base, these values place important constraints onp‐type doping levels and emitter injection efficiency in practical devices.

ISSN:0003-6951    

DOI:10.1063/1.102498

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

AlGaInP epitaxial layers grown at 690 °C by atmospheric pressure organometallic vapor phase epitaxy are investigated by transmission electron microscopy. For the first time, compositionally modulated and ordered structures are simultaneously observed in AlGaInP alloys. The ordering is of the CuPt type with ordering along the {111} directions. The ordered regions appear as plate‐like microdomains, while the composition modulation takes the form of a fine columnar constrast oriented along the growth direction. In addition, from the results of (001) plan‐view diffraction contrast examination, the principal strain direction associated with the modulation structures is found to be perpendicular to the growth direction and lies in the surface plane. Thus, it is concluded that the spinodal decomposition is initiated and developed on the surface during the growth of the AlGaInP epitaxial layers and, finally, forms the columnar structure.

ISSN:0003-6951    

DOI:10.1063/1.102499

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Stoichiometric reaction of copper dipivaloylmethanate [Cu(DPM)2] with the hydroxyl group (OH) on SiO2surface was studied by infrared spectroscopy. The stoichiometric ratio of reacted OH and Cu(DPM)2was estimated to be ∼2–3:1 from the absorbance of the OH and the CH stretching region. The ligand DPM was removed from the SiO2surface by treatment with water at 400 °C. The oxidation state of Cu remaining on the surface was proven to be +1 by x‐ray photoelectron spectroscopy.

ISSN:0003-6951    

DOI:10.1063/1.102500

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin‐film Josephson junctions with normal metal barriers using a Bi‐based highTcoxide superconductor were successfully fabricated. Bi2Sr2Ca1Cu2Oxfilms were used for both superconducting electrodes and Bi2Sr2Cu1Oyfor the barrier layer. The junction area of 20×40 &mgr;m2was defined by photolithography and Ar ion milling. These S/N/S‐type junctions clearly exhibited the ac Josephson effect under the irradiation of radio frequency waves of 12 GHz and more than 20 Shapiro steps were observed.

ISSN:0003-6951    

DOI:10.1063/1.103173

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The laser‐induced plasma plume created above a BiSrCaCuO superconducting target by a KrF laser beam (248 nm) is investigated by time‐resolved spectroscopy. The influence of the oxygen partial pressure on the ejection velocities of the ablated species and on the relaxation of atomic and molecular excited species is particularly studied.

ISSN:0003-6951    

DOI:10.1063/1.103155

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A study of field trapping by the incomplete Meissner effect was performed on YBa2Cu3O7−xat 77 K on both sintered and oriented grain samples. Fields of up toBT=1280 G have been trapped in small, oriented grain, planar samples. Circulating persistent current densities of up to 4800 A/cm2are calculated. Based on these values hollow cylinders of 2 cm i.d. will trap fields of 6000 G. Initial creep is about 10%/week for both types of samples. Creep rate varies as (BT/BT,max)2.BT, due to an external fieldB0, isBT∝(1−e−cB0/BT,max). Lamination and mosaic assembly steps for producing practical magnets have been performed.

ISSN:0003-6951    

DOI:10.1063/1.103207

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electrical properties of the interfacial layers between YBCO films and various substrates were studied usinginsituresistivity measurements. It was found that this method is sensitive to even a 10‐A˚‐thick interface layer. Moreover, it yields the resistivity of the interfacial layer and the YBCO film during deposition. For yttria‐stabilized zirconia, the interface has a very low resistivity. For MgO and sapphire the interface has a high resistivity; SrTiO3falls between these two cases. Sapphire shows a large reaction layer and evidence for nucleated growth, which are probably responsible for its relatively poor superconducting properties.

ISSN:0003-6951    

DOI:10.1063/1.103208

出版商:AIP    

年代:1990

数据来源: AIP