摘要:

The low‐energy (about 30 eV) ion etching of InP with an excellent vertical sidewall profile, smooth surface, and a high etch rate (more than 1000 A˚/min) has been demonstrated in an electron cyclotron resonance plasma using a Cl2/N2mixture. Surface analysis by x‐ray photoelectron spectroscopy and plasma diagnostics by optical emission spectroscopy suggest that the etching mechanism is dominated by the reduction of Cl neutral radical density by N2dilution and the formation of InN and P3N5due to the reaction between the atomic nitrogen in the Cl2/N2plasma and the InP substrate. The success of this technique appears to be based on a new InP dry etching concept which controls the volatility of PClx(x=1–5) products, thus balancing the desorption rate of InClx(x=1–3) products, in contrast to the conventional reactive ion etching method which enhances the desorption of nonvolatile InClxproducts by high‐energy ion bombardment. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359634

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Metallurgical and electrical properties of &bgr;‐phase PdAl Schottky metallizations onn‐GaAs after rapid thermal annealing for 20 s in the temperature range 500–1000 °C have been investigated using x‐ray diffraction, transmission electron microscopy, Auger depth profiling, film resistivity, and current–voltage measurement. The Al‐rich contacts were stable up to 900 °C whereas the Pd‐rich contacts were less stable. The thermal stability of &bgr;‐PdAl exhibited a sharp variation near the stoichiometric composition. The thermal stability of Pd‐rich contacts decreased with increasing Pd composition, and the interfacial reaction after high‐temperature annealing resulted in the formation of PdGa compound. The interface between Al‐rich PdAl film and GaAs substrate remained quite sharp even after 900 °C anneal. The variation of interfacial stability at high temperatures between &bgr;‐PdAl film and GaAs substrate is correlated to the compositional dependence of Al and Pd activities in PdAl within the &bgr;‐phase region. The Schottky barrier heights of Al‐rich PdAl contacts increased with annealing temperature. The barrier height enhancement in the annealed Al‐rich contacts can be attributed to the thin AlxGa1−xAs layer formed at the interface. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359635

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using statistical design of experiments, the effect of ultrasonic pre‐treatment on the nucleation density of diamond was studied. The parameters investigated included ultrasonic excitation power, concentration of diamond powder in water, duration of ultrasonic excitation, and duration of cleaning with water after ultrasonic excitation. Diamond films were deposited on silicon (100) substrates using microwave assisted plasma chemical vapor deposition. The nucleation density varied from 106nuclei/cm2to 109nuclei/cm2. The results illustrated that the dominant effect in ultrasonic pre‐treatment was seeding. Moreover, scratches caused by the seeds during the treatment enabled more seeds to be retained on the surface. Based on these results, an optimized ultrasonic pretreatment has been developed. The new procedure yields a uniform nucleation density of 109nuclei/cm2on silicon (100) substrates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359636

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoacoustic frequency heat‐transmission technique is used to study thermal and carrier transport properties in low‐doped silicon wafers. Amplitude and phase photoacoustic signals as a function of modulation frequency of incident optical beam are measured using different experimental conditions. The thermal diffusivity, coefficient of excess carrier diffusion, carrier lifetime, and the surface recombination velocity were determined by comparing experimental results and calculated theoretical photoacoustic signals. The suitability of the photoacoustic frequency heat‐transmission technique as a contactless diagnostic method is assessed in comparison with the more conventional photothermal deflection and photothermal modulated reflection techniques. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359637

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A calculation is described of the transient pulse response of a planar metal‐semiconductor‐metal photodetector consisting of Schottky contacts made to an active layer of semi‐insulating InGaAs:Fe that is supported on an InP:Fe substrate. The simulation uses a two‐dimensional, drift/diffusion calculation and includes external circuit elements. Realistic conditions are considered where the semi‐insulating material is represented by a two‐level compensation model with Fe as a deep acceptor and hole trap that compensates shallown‐type impurities. The calculated results are compared directly with experimental ones for micron‐scale devices described in the literature. The calculation gives a microscopic picture of how trapping controls particularly the falling side of the transient response, and it also shows how the measured performance of the device can reflect the influence of typical external circuit elements.

ISSN:0021-8979    

DOI:10.1063/1.359638

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The influence of the nonuniform photogeneration on the electric‐field distribution is considered for quantum‐well photodetectors under drift velocity saturation. We found that spatial nonuniformity of photogenerated electrons due to attenuation of the infrared flux induces strong electric‐field domains. The electric‐field domains formation is accompanied by degradation of the signal‐to‐noise ratio. We obtained that domain structures undergo realignment at certain threshold voltage as a result of feedback influence of the quantum well recharging on the photogeneration rates which in turn cause the additional electric‐field redistribution. The realignment manifests itself in a steplike change of photoconductive gain and quantum efficiency of photoabsorption at threshold bias voltage and is followed by considerable increase of generation–recombination noise. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359639

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electrical characteristics of ZnS:Mn alternating‐current thin‐film electroluminescent (ACTFEL) devices grown by atomic layer epitaxy are assessed as a function of the thickness of the phosphor layer using capacitance‐voltage (C‐V) and internal charge‐phosphor field (Q‐Fp) analysis. Deviations from the ideal in the measuredC‐VandQ‐Fpcharacteristics are ascribed to the generation of space charge in the phosphor layer during ACTFEL device operation.C‐Vovershoot deviations are correlated to space charge generation via a simulation employing a single sheet of charge model which assumes that the centroid of the generated space charge is located at a discrete sheet within the phosphor. Space charge generation in these atomic layer epitaxy (ALE) ZnS:Mn ACTFEL devices is ascribed to impact ionization of the zinc vacancy portion of chlorine‐zinc vacancy self‐activated defect complexes. A thermodynamic argument is provided which suggests that zinc vacancies are created via self‐compensation of ZnS when the ZnS is unintentionally doped with chlorine. It is contended that space charge generation could even be desirable in ALE ZnS:Mn ACTFEL devices because it leads to better aging stability and improved performance. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359640

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect of 3.5 keV electron irradiation on adhesion and contact resistivity of the Ag/YBa2Cu3O7interface has been studied using an evaporated silver layer onc‐axis oriented superconducting YBa2Cu3O7thin films. Electron doses ranged between 1016and 1018electrons/cm2. TheQ‐tip method of adhesion testing showed that even at the lowest electron dose adhesion is significantly improved. The contact resistivity of the interface was measured using a cross‐junction four‐point probe. Contact resistivity was unchanged at the lowest electron dose but increased as the electron dose increased. A theoretical model involving an electron irradiation damaged layer at the interface has been developed to explain measured contact resistivity changes. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359641

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The space‐charge limiting current for an intense, magnetized, relativistic electron beam injected into a grounded metallic pipe is investigated with a 2(1/2)‐dimensional particle‐in‐cell code. Comparisons between the simulation results, the well known Bogdankevich‐Rukhadze limiting current, and more recent theoretical estimates of the limiting current are presented. Transmitted currents ≳15% above those predicted by the Bogdankevich–Rukhadze and other limiting current estimates are observed. However, good agreement between the simulation results and the analytic estimates of Uhm [Phys. Fluids B5, 1919 (1993)] and Fessenden [Lawrence Livermore Lab. Rep. No. UCID‐16527 (1974)] is found. For an injected current above the limiting value, a virtual cathode is formed which alters the transmitted current density profile of the beam. A theoretical estimate of the magnitude of the transmitted current under this condition is compared with simulation results. The predicted transmitted current is found to be valid only for injected currents slightly above the limiting current. In addition, the transition between vacuum and ion‐focused‐regime transport, with and without an applied axial magnetic field is simulated. For ion‐focus‐regime densities (np∼nb), the effect of the virtual cathode in limiting the beam transmission is greatly diminished as expected. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359642

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electrodeposited magnetic Ni‐Fe films are used in storage devices and are applicable as magnetic sensors. In this work, we demonstrate the electrochemical conditions for deposition of permalloy Ni‐Fe nanocrystalline films onto InP(100) surfaces. The prepared Ni‐Fe films were analyzed by scanning electron microscopy to determine surface morphology and by Auger electron spectroscopy for compositional depth profiling. Permalloy films with bulk composition of 81% Ni and 18% Fe were obtained by electrodeposition at −1.2 V (versus standard calomel electrode) in a bath of 0.5 M NiSO4, 0.02 M FeSO4, 0.4 M H3BO3, pH=3. Transmission electron microscopy measurements show that these films consist of fcc Ni‐Fe nanocrystallites embedded in an amorphous matrix. The films also show good magnetic hysteresis loops, with low coercivity. The magnetic properties of these films are improved by an extended anneal at 100 °C. Interdiffusion occurred between Ni‐Fe and the InP substrate after the sample was heated to 300 °C, and consequently a loss of ferromagnetic behavior was observed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359643

出版商:AIP    

年代:1995

数据来源: AIP