摘要:

Spontaneous and ion‐enhanced etching reactions were investigated for the interaction of F atoms with Si(111) using modulated beam mass spectrometry. The F atoms were generated using a microwave plasma source which was compatible with ultrahigh vacuum. An impurity free surface, which was characterized by x‐ray photoelectron spectroscopy (XPS), could be obtained even after long exposures. The atom source and the experimental system are described in detail. It is shown that spontaneous etching at room temperature produces the stable gases SiF4, Si2F6, and Si3F8with SiF4being the dominant product. It is suggested that previous mass spectrometric investigations incorrectly ascribed SiF+and SiF+2peaks to a significant SiF2product, whereas these peaks should be assigned to Si2F6and Si3F8. As the surface temperature is increased, the relative contributions of the etch products SiF4, Si2F6, and Si3F8decrease while SiF2increases and eventually becomes the major product. Ion bombardment significantly enhances the production rate for all products. However, the type of mechanisms and magnitude of ion‐enhanced etching depend upon the type of product being observed. In contrast to spontaneous etching, ion‐induced etching produces a significant amount of SiF2as well as other products. Evidence is presented that suggests that chemical sputtering and an increased spontaneous etch rate are the primary mechanisms leading to ion‐enhanced etching. It will be shown that physical sputtering makes only a minor contribution under the conditions of these experiments.

ISSN:0734-211X    

DOI:10.1116/1.585593

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

SiO2and Si3N4films have been deposited at low temperatures by a new plasma enhanced evaporation process. The films are stoichiometric and have hydrogen contents below 1 at. %. For the electrical characterization metal–insulator–semiconductor diodes were fabricated and investigated before and after annealing in H2/N2atmosphere at 430 °C. Ellipsometric and capacitance–voltage measurements yield the dielectric constants which agree well with the theoretical values. From conductance–voltage characteristics the silicon–insulator interface state densityDitwas determined. After annealingDitamounts to 2×1011eV−1 cm−2for Si3N4and to 8×1010eV−1 cm−2for SiO2. In addition, the bulk resistivity and the surface resistivity of the deposited films were measured and compared with the values for films grown by conventional high temperature processes.

ISSN:0734-211X    

DOI:10.1116/1.585595

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The interaction at the metal–metal interface of the Al–Si–Cu/MoSi2bilayer system has been investigated as a function of the Cu concentration. The Al in the Al–Si–Cu alloy reacts with the MoSi2at temperatures above 400 °C. Al atoms diffuse into the MoSi2and the excess Si diffuses into the Al layer. After the reaction, the amorphous MoSi2becomes crystalline Mo(Al,Si)2. The excess Si in the MoSi2layer forms precipitates in the Al layer. The Cu concentration in the Al alloy affects the reaction rate with 1% Cu having the largest effect followed by 0.5% Cu and then 3% Cu. A model is presented that explains this phenomenon. The Al–Si alloy without Cu does not react with MoSi2below 450 °C.

ISSN:0734-211X    

DOI:10.1116/1.585596

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Growth temperature was found to play a crucial role in determining the structure of stoichiometric TiN films deposited on Si(100) by reactive magnetron sputtering. X‐ray diffraction, transmission electron microscopy (TEM), and reflection high‐energy electron diffraction were used to show that films deposited at substrate temperaturesTsranging from 700 to 1100 °C were polycrystalline, with either (100) preferred orientation or mixed (100) and (111) orientations. Films deposited using a two‐temperature technique were epitaxial with the relationships TiN(100)//Si(100) and TiN[011]//Si[011]but with considerable misorientation. The most highly oriented films were obtained when 45 nm was first deposited atTs=750 °C, followed by 250 nm at 1000 °C. High‐resolution cross‐sectional TEM studies showed that increasing the nucleation temperature above 750 °C led to random orientation of TiN lattice fringes relative to the Si lattice. This was explained by the small energy difference between oriented and misoriented TiN nuclei due to the large lattice mismatch (22%).

ISSN:0734-211X    

DOI:10.1116/1.585597

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Rutherford backscattering spectrometry and Auger electron spectroscopy are combined to study the interdiffusion behavior in alloyed Ni/Au/Te/Ni/GaAs ohmic contacts. The data are correlated to the results of electrical measurements to allow for a discrimination between the different ohmic contact models. Good ohmic behavior is found to coincide with the presence of a thin (≂200 Å) Te‐rich (5–10 at. %) layer in the substrate surface layers. This result and the diffusion data on nonohmic behaving contacts can most consistently be interpreted in the frame of the graded crystalline and/or amorphous heterojunction model.

ISSN:0734-211X    

DOI:10.1116/1.585598

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Mobility profiles in WnX‐LDD (lightly doped drain region) and WNX‐BPLDD (buriedp‐type buffer lightly doped drain region) GaAs metal–semiconductor field‐effect transistor (MESFET) with variousp‐buffer layers are discussed. The mobility profiles are evaluated using frequency dependent admittance studies. A slightly dopedp‐buffer layer seems to have no influence on the carrier concentration while there is a significant modification of the mobility profile at lower gate voltages. The channel drift mobility in BPLDD‐MESFETs with heavily implantedp‐buffer layers is degraded over the whole gate voltage swing. Mg‐p‐type implants have no effect on the carrier profile near its peak while the tail region is shifted to higher gate voltages. However, to observe a significant sharpening of the channel electron concentration profile a certain amount of Mg implantation dose seems to be necessary.

ISSN:0734-211X    

DOI:10.1116/1.585599

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We have grown graded‐index strained multiquantum‐well GaInAsP lasers by gas‐source molecular‐beam epitaxy (GSMBE) for a wavelength of 1.47 μm. The growth of graded layers and quantum wells by GSMBE is reported. X‐ray diffraction measurements of the laser structure were made and a simulation by dynamical diffraction theory gave good fitting. The threshold current densities were measured for 400‐ and 1000‐μm‐long broad‐area lasers, and they were 1350 and 780 A/cm2, respectively. We have also fabricated ridge waveguide lasers from the same sample.

ISSN:0734-211X    

DOI:10.1116/1.585600

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A novel GaAs quantum‐well (QW) negative differential resistance (NDR) device, prepared by molecular‐beam epitaxy (MBE), has been fabricated and demonstrated. TheS‐shaped NDR characteristics is attributed mainly to the impact ionization effect. First, the theoretical analysis based on a triangular barrier model is employed to study the influence of structure parameters on the barrier height. Then, the experimentalS‐shaped NDR behaviors are observed and analyzed for two‐terminal operation and three‐terminal operation, respectively. The successful usage of three‐terminal control gives flexible and wide application in switching circuits. Furthermore, the studied device exhibits a considerable reaction to illumination and temperature variation. Therefore, the studied NDR device may be used as a sensitive switch under excitation of light illumination and temperature variation.

ISSN:0734-211X    

DOI:10.1116/1.585601

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A laser‐induced dry etching process based on the generation of reactive species from the pyrolytic decomposition of selected metal alkyls is presented. Specifically, a focused, 514 nm cw laser to locally heat the surface of a GaAs sample in a dimethylzinc (DMZn) ambient is used. The DMZn dissociates pyrolytically at the hot surface, yielding reactive species that locally etch the GaAs. We have studied the process by characterizing etch rates in terms of laser dwell time, laser‐induced temperature, and DMZn pressure. Further, we have investigated the thermal dependence of the process, and have determined the boundaries of the parameter space for the successful avoidance of competing processes. Based on our experimental results and those of previous workers, we speculate that reactive methyl groups produced in the pyrolytic decomposition of DMZn react with the GaAs surface to produce volatile alkylated by‐products. Finally, the process to allow for the direct writing of surface‐relief features having smooth walls and submicron to micron‐scale depths have been optimized, which are potentially useful as electronic or optoelectronic device components. To demonstrate the utility of the etching process, riblike waveguiding structures in GaAs/Al0.3Ga0.7As multilayer substrates have been fabricated.

ISSN:0734-211X    

DOI:10.1116/1.585602

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The coverage‐ and structure‐dependent empty electronic states of Sb multilayers on nearly unrelaxed GaAs(110) and relaxed InP(110) have been investigated using inverse photoemission (IPES) and low energy electron diffraction. Two significant Sb‐derived empty states, termed features A and B, are used to characterize the evolution of ordered, metastable Sb multilayers and the ordered first monolayer. Feature A appears ∼0.30 and ∼0.35 eV aboveEFfor ordered metastable Sb multilayers onp‐GaAs(110) andp‐InP(110), respectively, while feature B appears at 2.0 eV for 1 ML of ordered Sb. Feature A resonates for photon energies of IPES near ℏωp=15.9 eV because radiative decay of a plasmon within the Sb film provides a decay channel that competes with the inverse photoemission channel. This resonance occurs for thicknesses greater than ∼3.5 ML for GaAs(110) and ∼2 ML for InP(110) for overlayers annealed at 475 K following Sb growth at 300 K. Structural studies reveal that the resonance features of IPES are correlated with metastable structures of the Sb layers. Very gradual relief of strained‐layer structures, coherent with (110) surfaces, may contribute to the existence of metastable phases for coverages below ∼10 ML. For Sb/GaAs(110), the metastable structures consist of long‐range‐ordered (110) domains with Sb crystallites between them. For Sb/InP(110), the metastable structures may be associated with a fairly continuous, periodic distribution of atomically corrugated (110) domains along [001], and the plane defined by the Sb zig–zag chains is not parallel to the unrelaxed (110) surface. These metastable structures may provide various coupling conditions for the momenta of the photon and the electron‐excited Sb plasmons.

ISSN:0734-211X    

DOI:10.1116/1.585603

出版商:American Vacuum Society    

年代:1991

数据来源: AIP