摘要:

The recombination process has been investigated in semi‐insulating GaAs Cr. The theoretical model was based on the Shockley–Read statistics considering two traps, the HL1 (Cr) and EL2, respectively. The trap concentrations and the carrier lifetimes have been determined from the dependence of both the photomagnetoelectric effect short‐circuit current and the photoconductance on the illumination intensity.

ISSN:0021-8979    

DOI:10.1063/1.346749

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Chemical bonding and reactions at the Fe/Si interface have been studied as a function of Fe overlayer thickness and annealing temperature. The chemical properties (composition, electronic structure, and reactivity) were observed under ultrahigh vacuum conditions using x‐ray photoemission, ultraviolet photoemission (UPS), and Auger electronic spectroscopy. Both core line and valence‐band states have been measured. At room temperature, intermixing of atoms across the clean Fe/Si interface occurs. In the initial stage the Fe2p3/2core line shifts 0.4 eV to a higher binding energy relative to pure Fe metal. This is nearly the same as the chemical shift of the Fe2p3/2core line in FeSi2. With increasing coverage, the Fe2p3/2core line shifts decrease and subsequently approach that of pure Fe metal. In the meanwhile, the Fe2p3/2core line shapes changed gradually with greater width and asymmetry upon metal deposition. At the lower coverage, the UPS spectra are dominated by a broadband, but at high coverage, two peaks corresponding to Fe3dand Fe3d‐Si3pbonding are observed. Upon deposition,the nonbondingd‐state peak shifts to the Fermi level and the spectrum becomes that of pure Fe metal. All these results are discussed in the context of an interstitial diffusion model between Si and Fe at the Fe/Si interface.

ISSN:0021-8979    

DOI:10.1063/1.346750

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A measurement technique and analysis are presented for the accurate determination of the capture cross sections of the interface states in metal‐oxide‐semiconductor (MOS) structures. The technique utilizes the interface‐trap‐filling kinetics during measurements by energy‐resolved deep level transient spectroscopy (DLTS). High accuracy is attained by accounting in the analysis for the charge‐potential feedback effect which is a unique feature of the MOS structure and which presents a critical difficulty in the DLTS measurement of capture cross sections in MOS devices. The accurate measurement of the capture cross sections obtained in this work allows us to study several electronic properties of the Si‐SiO2interface including (i) the behavior of the capture cross sections of interface states created by high‐field stress on MOS devices, and (ii) the determination of the capture cross section of dangling bonds at the ⟨100⟩‐oriented Si‐SiO2interface. Finally, the possibility of determining the degeneracy factor of the interface states is questioned.

ISSN:0021-8979    

DOI:10.1063/1.346751

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Injection over and through heterojunction barriers is becoming increasingly more important in modern electronic devices. We consider the properties of graded AlxGa1−xAs heterojunction barriers using a self‐consistent ensemble Monte Carlo method. In this paper, we consider barriers with two doping levels, 1×1015cm−3and 1×1017cm−3, and two barrier heights, 100 and 265 meV. The 100‐meV barrier resulted in small rectification at room temperature whereas the higher barrier exhibited considerable rectification. In both cases the structure with the lower doped barrier has resulted in a smaller current in both forward and reverse regions due to space‐charge effects. The energy and momentum distribution functions deviate from a Maxwellian distribution inside the barrier region and in general show two peaks: one is comprised mainly of electrons near equilibrium and the second arises mainly from ballistic electrons. The higher doped structure resulted in a faster electron relaxation toward equilibrium as a function of position because the electric field decreases rapidly in the barrier region.

ISSN:0021-8979    

DOI:10.1063/1.346728

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have demonstrated the viability of depositing a thick Au bonding pad on top of Pt/Ti contacts on bothp‐InGaAs andn‐InP within a single evaporation prior to heat treatment. This eliminates the usual post‐sinter Au plating process. In particular, Au (500 nm)/Pt (60 nm)/Ti (50 nm) common contacts to Zn‐doped 5×1018cm−3p‐In0.53Ga0.47As and S‐doped 1×1018cm−3n‐InP were formed within a single pumpdown electron‐gun evaporation and subsequently a single sintering process by means of rapid thermal processing. The lowest resistivity of these ohmic contacts were found to be 0.11 and 0.13 &OHgr; mm (5.5×10−7and 8×10−6&OHgr; cm2) for thepandncontacts, respectively. These values were achieved as a result of heating at 450 °C for 30 sec. This heat treatment caused a limited reaction at the Au‐Pt and Pt‐Ti interfaces, which did not lead to any significant intermixing of the Ti and Au. Thus, no significant indiffusion of the Au thorough the Pt barrier was observed and contact degradation did not occur. The stress of the as‐deposited trilayer structure on InP was found to be 3×108dyne cm2tensile and increased to about 2×109dyn cm2as a result of the rapid thermal processing at 450 °C

ISSN:0021-8979    

DOI:10.1063/1.346706

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Nanometer scale features (75–1000 nm) were defined on GaAs/AlGaAs heterostructure surfaces by electron beam patterning. The use of low‐voltage, helium‐ion damage laterally confined the two dimensional electron gas to these patterned areas. Electrical characterization of the conducting channels as well as the ion‐damaged material outside the patterned areas included measurements of the Hall mobility, the carrier concentration and the sheet resistance at various temperatures. The major problem encountered with the nanowires was an increase in the wire sheet resistance over the as‐grown value at 4.2 K. Process‐related factors contributed to this increase, but the most probable cause is boundary scattering at the lateral edges of the nanowires.

ISSN:0021-8979    

DOI:10.1063/1.346707

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The model for simulating high‐frequency capacitance‐voltage characteristics of amorphous/crystalline heterojunctions has been developed, where the high frequency indicates a frequency higher than the reciprocal of the dielectric relaxation time of the amorphous semiconductor. The physical background of the space‐charge density of the amorphous film and the built‐in voltage of the heterojunction, which are experimentally obtained from the heterojunction‐monitored capacitance method, is discussed using the calculated results.

ISSN:0021-8979    

DOI:10.1063/1.346708

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A glass of nominal Bi1.5Pb0.5Sr2Ca2Cu3Oxcomposition, prepared by rapid quenching of the melt, showed a glass transition temperature of 383 °C, crystallization temperature of 446 °C, melting temperature of 855 °C, and bulk density of 5.69 g/cm3in air. The activation energy for crystallization of the glass has been estimated to be 292 kJ/mol from nonisothermal differential scanning calorimetry. On heating in oxygen, the glass showed a slow and continuous weight gain starting at 530 °C which reached a plateau at 820 °C. The weight gained during heating was retained on cooling to ambient conditions indicating an irreversible oxidation step. The influence of annealing conditions on the formation of various phases in the glass has been investigated. The Bi2Sr2Ca0Cu1O6phase crystallized out first followed by formation of other phases at higher temperatures. The high‐Tcphase, isostructural with Bi2Sr2Ca2Cu3O10, was not detected below 840 °C, but its fraction increased with the annealing time at 840 °C. A sample annealed at 840 °C for 243 h in air and furnace cooled showed the highestTc(R=0) of 107.2 K and a narrow transition width, &Dgr;Tc(10%–90%), of 2 K. The high‐Tcphase does not seem to crystallize out directly from the glass but is rather produced at high temperature by reaction between the phases formed at lower temperatures. The kinetics of 110‐K phase formation was sluggish. It appears that the presence of lead helps in the formation and/or stabilization of the 110‐K phase.

ISSN:0021-8979    

DOI:10.1063/1.346709

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Plasma‐enhanced organometallic chemical vapor deposition process has been developed to prepare highTcsuperconducting films. The volatile organic precursors of Y(fod)3, Ba(hfa)2, and Cu(hfa)2were decomposed with a microwave discharge plasma. Optical emission spectroscopy was used to determine the identity of the species produced during the vaporization and decomposition process. In this process, Y, Y+, Ba, Ba+, Cu, and Cu+species were detected. After annealing in air, the films deposited on the (100) SrTiO3substrate had preferential orientation of the crystallinec‐axis perpendicular to the substrate surface. The characterization of this process is discussed comparing a hollow cathode YBaCuO plasma with the laser ablation experiments published.

ISSN:0021-8979    

DOI:10.1063/1.346710

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

High‐temperature superconducing Tl‐Ca‐Ba‐Cu‐O (TlCaBaCuO) thin films were fabricated by rf magnetron sputtering on strontium titanate (SrTiO3) substrates. Thin films of 0.5–0.7‐&mgr;m thickness were deposited by pure argon sputtering from a single composite powder target of Tl2Ca2Ba2Cu3Oxat an rf power of 250 W and a pressure of 5 mTorr. As‐deposited thin films were sintered and annealed in a thallium‐rich ambient to obtain superconductivity with a zero resistance temperature (Tc0) at 107 K. X‐ray diffraction results showed highlyc‐axis oriented films with Tl2Ca2Ba2Cu3Ox(2223) and Tl2Ca1Ba2Cu2Ox(2122) phases present. Auger electron spectroscopy survey and depth profiles were performed to determine the compositional uniformity and impurity contents of the thin films. X ray photoelectron spectroscopy high‐resolution spectra were obtained at the surface, in the bulk, and near the interface with the substrate. Our XPS results support two possible mechanisms for the creation of holes in the TlCaBaCuO compound: (1) partial substitution of Ca2+for Tl3+and (2) charge transfer from Tl3+to the CuO layers resulting in a valence of Tl between +3 and +1 states and the creation of holes in the CuO layers. In addition, a wet chemical etching process was developed for patterning the as‐deposited TlCaBaCuO thin films. A 125‐&mgr;m‐wide line was formed using standard photolithography and wet chemical etching which, after heat treatments, showed superconductivity with aTc0of 80 K.

ISSN:0021-8979    

DOI:10.1063/1.346711

出版商:AIP    

年代:1990

数据来源: AIP