摘要:

We report the first direct measurement of electron storage time at the AlxGa1−xAs/GaAs interface as a function of Al mole fractionx. Storage capacitors withx=0.4, 0.6, 0.8, and 1.0 were fabricated and their inversion layer electron retention times measured. The optimal mole fraction for electron retention is in the range 0.4≤x≤0.6.

ISSN:0003-6951    

DOI:10.1063/1.102229

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Reflection high‐energy electron diffraction (RHEED) intensity oscillations have been used during molecular beam epitaxy (MBE) to accurately determine threshold layer thicknesses for two‐dimensional (2D) growth of InxGa1−xAs on GaAs for a wide range of substrate temperatures and indium compositions. InxGa1−xAs/GaAs single quantum wells were also grown by MBE and studied using low‐temperature photoluminescence (PL) spectroscopy. PL peak energy, intensity, and linewidth measurements provided information on the critical layer thicknesses for the formation of dislocations which, under our experimental conditions, were the same as the threshold layer thicknesses for 2D growth measured from the damping behavior of RHEED intensity oscillations.

ISSN:0003-6951    

DOI:10.1063/1.102279

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Measurement of dopant density in silicon with lateral resolution on the 200 nm scale has been demonstrated with a near‐field capacitance technique. The technique is based upon the measurement of local capacitance between a 100 nm tip and a semiconducting surface. Lateral dopant imaging is achieved by the measurement of the voltage‐dependent capacitance between tip and sample due to the depletion of carriers in the semiconductor, as the tip is scanned laterally over the surface. Measurements of dopant density have been demonstrated over a dopant range of 1015–1020cm−3. Capacitance‐voltage measurements have been made on a submicrometer scale.

ISSN:0003-6951    

DOI:10.1063/1.102312

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Thin (11.4 nm) gate quality silicon dioxide films were subjected to high‐temperature (850–1150 °C) rapid thermal nitridation cycles in ultrapure ammonia. Secondary‐ion mass spectroscopy and neutron depth profiling results indicate a significant level of nitrogen diffusion into the silicon substrate. After stripping the dielectric layers, Schottky diode studies were performed using an electrolyte‐based technique. We found, for the first time, the formation of nitridation‐induced ultrathin (less than 60 nm)n‐type layers at the top surface of nominallyp‐type silicon substrates used in the study. A nitrogen‐oxygen donor complex formation mechanism is invoked to explain the presence of the ultrathinn‐type layers.

ISSN:0003-6951    

DOI:10.1063/1.102230

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We use a combination of electrical, optical, and structural characterization techniques to determine the critical layer thickness of strained Ga1−xInxAs/InP quantum wells. Well compositions covering the entire range of strain available, from −3.8% (GaAs) to +3.2% (InAs), were investigated. We find that the critical layer thickness in this material system is unambiguously described by the classical Matthews and Blakeslee force balance model [J. Cryst. Growth27, 118 (1974)]. Reverse leakage current of strained‐well samples grown in ap‐i‐nconfiguration is shown to be the most direct and reliable measure of the pseudomorphic limit.

ISSN:0003-6951    

DOI:10.1063/1.102231

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Semiconducting &bgr;FeSi2has been successfully grown on a Si (111) substrate. It has been proven that under ultrahigh vacuum conditions, the solid phase epitaxy temperature can be lowered to ∼800 K, where only the &bgr;FeSi2phase is stabilized. The disilicide formation was monitoredinsituby various surface‐sensitive techniques such as low‐energy electron diffraction, Auger electron spectroscopy, and ultraviolet photoelectron spectroscopy. The epitaxial relationships were ascertained by transmission electron diffraction and microscopy including high‐resolution cross‐sectional image. The results show the epitaxy of &bgr;FeSi2 (110) and (101) planes parallel to the Si (111) plane. The disilicide‐silicon heterojunction displays an atomically abrupt interface.

ISSN:0003-6951    

DOI:10.1063/1.102313

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A new mechanism is proposed for Si incorporation in GaAs‐on‐Si heteroepitaxial layers grown by metalorganic chemical vapor deposition. This mechanism involves gas phase transport of the Si to the heteroepitaxial layers during growth. This mode of Si uptake could operate in addition to the previously proposed mechanism of Si incorporation by enhanced diffusion from the heterointerface through defects in the GaAs layer.

ISSN:0003-6951    

DOI:10.1063/1.102232

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report electrical and optical properties of very high purity GaAs epilayers grown by low‐pressure metalorganic chemical vapor deposition using AsH3and triethylgallium as As and Ga sources. An electron mobility of 335 000 cm2/V s at 38 K has been measured for a 12‐&mgr;‐thick layer.

ISSN:0003-6951    

DOI:10.1063/1.102233

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The chemical compositions of surface and bulk regions of pulsed laser deposited YBa2Cu3O7−xfilms on SrTiO3(001) substrates were examined. From the relative intensities of the surface and bulk components of the Ba 3dand Ba 4dspectra taken at different take‐off angles and different escape depths [using Al K&agr; (1486.6 eV) and Mg K&agr; (1253.6 eV) excitations], we have concluded that there is a nonsuperconducting surface layer of 1 nm thickness with a composition of BaCuO2. This layer contains oxygen with a photoelectron binding energy of 531 eV, and Cu2+ions. A superconducting film which was only 8 nm thick also had a layer of 1 nm thickness. By detecting the substrate Ti signal through this film, and ruling out a high density of pinholes, we provide evidence that the x‐ray photoelectron spectroscopy data contain information from the superconducting phase. A polycrystalline pellet scraped in vacuum had a similar surface layer, which was only 0.4 nm thick.

ISSN:0003-6951    

DOI:10.1063/1.102314

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Directionally solidified superconducting Bi‐Sr‐Ca‐Cu‐O thick films have been fabricated by laser zone melting. Highly aligned grain structures were obtained. Films with no post‐processing anneal showedTc(R=0)=82 K and transport critical current densitiesJcas high as 450 A/cm2at 77 K and 5400 A/cm2at 60 K. After annealing for 65 h at 850 °C,Tcincreased to 85 K, and the best sample showedJc=2200 A/cm2at 77 K and 11 200 A/cm2at 60 K.

ISSN:0003-6951    

DOI:10.1063/1.102315

出版商:AIP    

年代:1989

数据来源: AIP