摘要:

Reduction in the reverse‐bias current in low‐temperature‐annealed siliconpnjunctions has been studied. It has been shown that the transition region existing underneath the ion‐implantation‐generated amorphous layer and the contamination incorporated into this region play a decisive role in determining the reverse current level. In order to minimize the contamination involvement into the transition region, ultraclean ion‐implantation technology has been developed. Ion implantation was carried out under a UHV (5×10−10Torr) condition in order to minimize the recoil implantation of adsorbed contamination at the surface. The contamination due to the high‐energy ion‐beam sputtering of component parts in the ion implanter has also been suppressed. As a result, a low reverse‐bias current level of about 1.2×10−7A/cm2has been obtained for arsenic‐implantedn+pjunctions annealed at 550 °C, which is more than two orders of magnitude smaller than that previously reported. The stress compensation technology employing combined implantation of phosphorus and arsenic has also been shown to be very effective in reducing the lattice strain and in suppressing the damage generation.

ISSN:0021-8979    

DOI:10.1063/1.344529

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Experimental characteristics of ultrashallown+pjunctions manufactured by vacuum evaporation of antimony (Sb) and silicon (Si), followed by heat treatments to recrystallize the amorphous silicon, are presented. It is found that then+pjunction is located less than 300 A˚ inside the crystalline silicon and that all Sb is redistributed within the regrown film. Comparisons with Schottky (Sb‐Si) diodes show that with a heat treatment at 900 °C, the diodes convert fully from Schottky type ton+ptype. Furthermore, normally off‐type junction field‐effect transistors have been fabricated using thesen+pjunctions as gate junctions, and the characteristics are presented together with data concerning threshold voltage variations. Also, the subthreshold characteristics of these junction field‐effect transistors are presented. The behavior in the subthreshold region is found to be excellent.

ISSN:0021-8979    

DOI:10.1063/1.344530

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Beryllium was ion implanted into GaAs that had been previously amorphized by a liquid‐nitrogen‐temperature arsenic implant. After rapid thermal annealing complete electrical activation of the beryllium was indicated by carrier profiles measured by van der Pauw–Hall and electrochemical capacitance‐voltage techniques. Diffusion of the beryllium profile as determined by secondary‐ion‐mass spectroscopy was suppressed in the arsenic‐preamorphized layer. The combined effects of an amorphous layer to suppress ion channeling and excess arsenic to suppress diffusion resulted in a very abrupt beryllium‐implanted layer. The high electrical activation of the ion‐implanted beryllium represents what we believe is the first successful attempt to activate an impurity implanted into a preamorphized gallium arsenide layer.

ISSN:0021-8979    

DOI:10.1063/1.344531

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Photoreflectance is used to measure AlxGa1−xAs composition, and to determine carrier concentrations in Si‐doped AlGaAs epilayers capped with GaAs. Undoped caps are generally depleted, and do not show a usual GaAs photoreflectance. However, photoreflectance from the cap/(doped AlGaAs) interface produces a broad signal which distorts the entire spectrum, making it hard to locate the GaAs and AlGaAs band edges precisely. A similar broad signal from modulation‐doped heterostructures is apparently associated with samples that show the presence of two‐dimensional electron gas.

ISSN:0021-8979    

DOI:10.1063/1.344532

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

High‐quality amorphous hydrogenated germanium has been deposited using the diode rf glow discharge method out of a gas plasma of GeH4and H2. The optical, electrical, and structural properties of this material have been extensively characterized. The optical and electrical properties are all consistent with material containing a low density of defect related states in the energy gap. In particular, this material has an &eegr;&mgr;&tgr;=3.2×10−7cm2/V, ratio of photocurrent to dark current of 1.3×10−1, and flux dependence of the photocurrent with &ggr;=0.79 at 1.25 eV measured using photoconductivity, a &mgr;&tgr;=4×10−8cm2/V measured using time of flight, an Urbach energy of 51 meV and &agr; at 0.7 eV of 8.3 cm−1measured using photothermal deflection spectroscopy, a dangling bond spin density of 5×1016cm−3measured using electron spin resonance, photoluminescence with a peak energy position of 0.81 eV and full width at half maximum of 0.19 eV, an activation energy of 0.52 eV and &sgr;0of 6.1×103(&OHgr; cm)−1measured using dark conductivity, and anE04band gap of 1.24 eV measured by optical absorption. The structural measurements indicate a homogeneous material lacking any island/tissue and columnar structure when investigated using transmission and scanning electron microscopy, respectively. Hydrogen concentrations calculated from infrared and gas evolution measurements can only by reconciled by postulating a large quantity of unbonded hydrogen whose presence is confirmed using deuteron magnetic resonance. The bonded deuterium component, as seen in this film using DMR, has a spin‐lattice relaxation time of the order of 4000 s. The differential scanning calorimetry measurement shows crystallization occurring at 421 °C and the presence of large compressive stresses has been confirmed using a bending‐beam method. The experimental details necessary to interpret the quantities quoted here are set out in the text which follows. It is considered that the very good optical and electrical properties of this as yet unoptimized material are directly related to the structural properties detailed above.

ISSN:0021-8979    

DOI:10.1063/1.344533

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of electron‐hole pair recombination near the silicon/silicon dioxide interface of aluminum‐gate metal‐oxide‐semiconductor capacitors have been studied. For the first time, electron‐heating‐induced trap generation and interface state creation is separated from those defects created through electron‐hole pair recombination. The midgap interface state density is observed to increase linearly with the number of recombination events and approaches saturation in the mid 1011eV−1 cm−2range for trapped hole densities greater than about 1012cm−2. However, the total integrated interface state density, although showing a similar net increase to that of the midgap interface state density, does not saturate for the largest trapped hole densities introduced in this work. For hot‐electron‐induced defects, a dramatic increase in the interface state generation rate is observed for average electric fields above a threshold of 1.5×106V cm−1. An increase in the electron trapping rate above the heating threshold is also detected at both the cathode and anode interfaces. The rate is found to be approximately 10−5traps or interface states generated per injected electron for average electric fields below the heating threshold, while above the threshold this rate increases by an order of magnitude. These rates were measured for injected electron fluences as low as 10−3C cm−2. These high trapping and interface state generation rates are believed to be due to the high concentration of hydrogen (or hydrogen‐related species) in these films.

ISSN:0021-8979    

DOI:10.1063/1.344534

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Among the most critical parameters in the fabrication of rf‐sputtered SrTiO3films is the argon/oxygen ratio in the sputter gas and the substrate temperature, both during sputtering and during postannealing. After sputtering at 500 °C, SrTiO3layers on Al2O3substrates are partially crystalline. In this case the SrTiO3lattice is enlarged compared to the bulk material. With increasing temperatures of postannealing, the crystallites grow and the lattice shrinks. In particular, films that are sputtered with a sputter gas containing oxygen show an additional phase of TiO2when they are annealed at temperatures of more than 1000 °C. This paper shows for the first time results of the investigation of sputtered SrTiO3films on Al2O3substrates as a function of oxygen partial pressureP(O2). The measurements performed on the sputtered films indicate semiconducting properties in agreement with the bulk material: At temperatures between 700 and 1100 °C the electrical conductivity of sputtered layers changes fromp‐type ton‐type as the oxygen partial pressure decreases from 1 to 10−15bar. The enthalpy of oxidation in the SrTiO3films is 1.24 eV, and the energy gap is 3.30 eV. These values are in agreement with those reported for bulk materials.

ISSN:0021-8979    

DOI:10.1063/1.344535

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The structural properties of a high‐temeprature superconducting textured YBa2Cu3O7−xthin film on a SrTiO3(100) substrate have been studied by reflection x‐ray pole‐figure methods, which can elucidate the degree of preferred orientations of the crystallites in polycrystalline materials and the relative orientations and lateral lattice alignments of the film with respect to the substrate. The specimen was fabricated on a SrTiO3(100) substrate by rf diode sputter deposition and subsequent furnace annealing in flowing oxygen. The film was found to be more preferentiallyaaxis oriented thancaxis oriented with a grain ratio of about 4:1. Thea‐axis‐oriented grains are heavily twinned and the twinning structure is reflection about the (013) plane. The pole figures of thec‐axis‐oriented grains are consistent with the (110) reflection twinning structure. Nevertheless, the crystal axes of both types of oriented grains are aligned with those of the substrate. In addition, the interface matching of the film with respect to the substrate is discussed.

ISSN:0021-8979    

DOI:10.1063/1.345831

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

During the transition of a superconducting winding, most of the dissipated power heats the conductors causing the propagation of the normal zone. Some part of the dissipated power is also transferred into the surrounding insulation. Due to the weak thermal conductivity of the insulating material, a certain amount of time is required for this heat to diffuse. The propagation front thus carries with it a wake of thermal diffusion, which raises the question of how much insulator should be taken into account in calculating the propagation velocity. Postulating the existence of such a velocity, we derive a model for the thermal behavior of an insulated layer of composite multifilament superconductors during the transition phase. The two‐way Laplace transform is used to solve the equations for temperature diffusion/propagation in the conducting and insulating media. This yields an implicit equation for propagation velocity, which is then written in a dimensionless form. We next investigate two limiting cases, deriving in each case a simplified formula for propagation velocity. Last, we complete the analytical solution of our problem by computing the originals of the temperature profiles.

ISSN:0021-8979    

DOI:10.1063/1.345832

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have investigated the effect of 1‐MeV electron irradiation up to a total dose of 5.7×1017electrons/cm2at room temperature on YBa2Cu3Oxwith gold bead contacts made by the melting technique. We measured the superconducting transition temperatureTc, the critical current densityJcat 77 K, the normal‐state resistivity, and the contact resistance for gold bead contacts as a function of fluence on the same samples without disturbing the contacts.Tcremained constant at 91 K, andJcat 77 K remained constant around 90 A/cm2. The normal‐state resistivity increased systematically by about 15% for the total dose. Finally, the surface contact resistance at 77 K remained less than 4.2 &mgr;&OHgr; cm2throughout the radiations. These studies took place over an 8‐month period, and subsequent measurements indicate that the results are definitely due to radiation effects and not aging effects. Since the total dose represents 120 years of electron exposure in geosynchronous orbit, we conclude that the superconductor YBa2Cu3Oxwith gold bead contacts would perform well in a space environment of electron irradiation.

ISSN:0021-8979    

DOI:10.1063/1.345833

出版商:AIP    

年代:1990

数据来源: AIP