摘要:

There is increasing technological interest in using Cl2and Cl‐containing compounds in the dry plasma etching of III–V semiconductors. This paper presents a study of the ion‐assisted etching of GaAs by Cl2using a modulated ion beam technique to gain insight into the kinetic mechanism of this process. The etching rate increases with increasing ion energy (0.3–3 kV) and depends linearly on ion flux (1.0–10.0×1014ions cm2 s). The etching rate increases with increasing Cl2pressure up to a saturation limit near 2×10−6Torr. This saturation limit is independent of the ion flux coincident on the surface within the range studied. The ion‐enhanced etching rate decreases with increasing sample temperature over the range 300–500 K. Major etch products are AsCl3and GaCl2(and possibly GaCl), and the time dependence of the increase in these mass spectrometer signals following the initiation of the ion pulse is consistent with all of the products having a most probable translational energy of ∼0.14 eV. There is an additional delay in the appearance of the AsCl3signal which roughly corresponds to a first order reaction with an associated time constant of 1.1 ms. One possible kinetic mechanism for the ion‐enhanced etching is proposed which involves the surface reactions of Ga and AsCl with adsorbed chlorine. In this model, the ∼1 ms delay in the appearance of the AsCl3is attributed to the lifetime of potential energy excitation caused by the ion.

ISSN:0021-8979    

DOI:10.1063/1.336241

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Thermionic emission measurements have been used to determine the work function (&Jgr;) of pure and oxidized uranium samples between 1100 and 1300 K; Auger electron spectroscopy (AES) was used to verify the cleanliness and compositions of the samples. It was found that impurities present in ppm amounts in the bulk U segregated to the surface upon heating and had an appreciable effect on the zero‐field emission currents as well as the slopes of the Schottky curves obtained at various temperatures. A combination of ion‐sputtering and ultrahigh vacuum (UHV) annealing at high temperatures was successful in reducing the total impurity level on the hot surfaces to 5%. At this low concentration of impurities, well‐behaved Richardson line plots were obtained withA=135 A cm−2 K−2and &Jgr;=3.54 eV for pure U andA=128 A cm−2 K−2and &Jgr;=3.19 eV for UO2. The Schottky coefficients for clean U approached their ideal values at fields >400 V/cm.

ISSN:0021-8979    

DOI:10.1063/1.336242

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

High‐purity, lightly Si‐doped (&mgr;77∼70 000–126 000 cm2/V s andn77∼2–8×1014cm−3) molecular beam epitaxy (MBE) GaAs layers have been characterized using variable‐temperature Hall effect andC‐Vmeasurements, photothermal ionization spectroscopy, low‐temperature photoluminescence (PL), and deep level transient spectroscopy (DLTS). The spectroscopic measurements of the residual donors and acceptors indicate that the pronounced increase in carrier concentration which is observed with increasing As flux (for a constant Ga flux) results from incorporation of additional residual S donors from the As source material, and not from reductions in the Si acceptor concentration or residual C acceptor concentration. The increase in carrier concentration with As flux is considerably more pronounced when using an alternative source of As, which introduces both S and 3 additional donor species. The C acceptor concentration increases with As flux using either As source, although the increase is much stronger with the alternative source. The dependence of C concentration on the As source implies that the As source itself contributes at least part of the C background. The Si acceptor concentration is negligible for the range of growth conditions that were used. Close compensation between the residual S donors and C acceptors may account for the high resistivity previously observed in undoped samples grown in this system using the purer As source. The PL data exhibit very weak ‘‘defect’’‐related emissions in the 1.504–1.512 and 1.466–1.482 eV ranges; evidence is presented supporting the existence of a correlation between these two sets of peaks, in agreement with the work of Briones and Collins.Temperature and excitation intensity‐dependent PL measurements are used to demonstrate conclusively that the peaks in the 1.466–1.482 eV range are donor‐to‐acceptor and band‐to‐acceptor in nature, involving normal shallow donors and at least four different acceptor levels whose exact origin is unknown. The ‘‘defect’’ peak intensity is larger in the less pure material which contains more C, implying that the ‘‘defects’’ may be C related. Several electron traps including M1, M3, and M4 are observed in the DLTS spectra, and theC‐Vmeasurements give a total trap concentration of ∼3×1013cm−3.

ISSN:0021-8979    

DOI:10.1063/1.336243

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

High‐quality Cd(Se,Te) in two compositions were synthesized using the modified Bridgman technique. The Se‐rich crystals had the hexagonal structure while the Te‐rich phase consisted of crystals with cubic packing. Their quality could be gauged from the high‐electron mobility and their low resistivity which suited the purpose of their synthesis, i.e., for high‐efficiency photoelectrochemical cells. Photoelectrochemical etching was employed, which resulted in a heavily pitted surface with the density of the etch pits exceeding 109cm−2. Quantum efficiency of the semiconductor/aqueous polysulfide interface increased considerably after photoetching. Solar to electrical conversion efficiencies in excess of 12% were obtained. Photoluminescence spectrum was measured for the two crystals prior to and after photoetching. The emission maximum is near the calculated band gap. The decline in the luminescence intensity, after photoetching, is attributed to the corrugation of the surface and the reduced density of the donor state near the semiconductor surface, which increases the thickness of the space‐charge layer (dead layer model).

ISSN:0021-8979    

DOI:10.1063/1.336314

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The effect of the type of power cycle upon the amount of output electrical work for a pyroelectric converter has been measured. Output electrical energy densities are reported for ceramic lead zirconate modified with Sn4+and Ti4+in the execution of a variety of thermal‐electrical cycles. The effect upon the energy density due to changes in the voltage cycle limits and changes in the load resistance were also studied. A conversion cycle which is an electric analog of the Ericsson cycle is shown to yield the largest output energy density (100 mJ/cm3for a 12.6 K temperature excursion and a 28‐kV/cm electric field excursion).

ISSN:0021-8979    

DOI:10.1063/1.336244

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This paper examines the effects of thermal loading and time history upon the thermal stresses developed in lithographic mask structures as would be expected under irradiation by intense soft x rays. The objective of this work was to examine the phenomenology of the interaction and to evaluate the limits placed upon mask dosage. The mechanics of mask failure are examined in terms of single pulse and cumulative, or fatigue, effects. A number of prototypical mask structures are investigated, which show that the application of intense pulsed sources to x‐ray lithography does not reduce the potential utility of the techique. However, it is shown that the estimated damage thresholds do impact the operating conditions chosen for optimal production rates and mask lifetime.

ISSN:0021-8979    

DOI:10.1063/1.336245

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This paper addresses the issue of the dynamic response of thin lithographic mask structures to thermally induced stress fields. In particular, the impact of repetitively pulsed x‐ray sources are examined: the short duration (1–100 nsec) pulses induce large step changes in mask temperatures, which can, in turn, induce a dynamic response. The impact of conductive cooling of the mask is to reduce the repetitively pulsed problem to a series of isolated nearly identical thermal impulses of duration approximately equal to the cooling time. The importance of self‐weight and prestress is examined, and an analysis of the nonlinear dynamic response to thermal impulses is described.

ISSN:0021-8979    

DOI:10.1063/1.336246

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The preparation and properties of Cd‐diffusedp‐nhomojunction InGaAsP photodiodes designed specifically for operation at the 1.3‐&mgr;m wavelength are described. At a reverse bias of 10 V, the dark current of these diodes was as low as 15 pA. The peak responsivity at 1.3‐&mgr;m wavelength was 0.7 A/W. An impulse response (full width at half maximum) of 60 ps and a 3‐dB bandwidth of 5.5 GHz were achieved.

ISSN:0021-8979    

DOI:10.1063/1.336247

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this paper it is shown that the optical determination of free‐carrier concentrationN0in 5–10 &mgr;m thick epitaxial layers ofn‐type silicon grown on N+or N−substrates is possible for concentrations ≥2×1016cm−3by measuringp‐polarized reflected lightRpnear the Brewster angle at a wavelength &bartil;10 &mgr;m. Good crystallinity, constant concentration profiles normal to the surface, as well as relatively small differences in the index of refraction with respect to the substrate are essential requirements in order to get high resolution. Good agreement with the angular derivative ofRpis obtained.

ISSN:0021-8979    

DOI:10.1063/1.336248

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Ion velocity distributions generated in a 0.53‐&mgr;m laser‐produced plasma are studied with a Thomson parabola diagnostic at 5×1013W/cm2. Ions are observed in a narrow energy range. However, for velocities >4×105m/s the distributiondN/dVdecreases exponentially and the temperatures deduced from these distributions are in good agreement with those given by x‐ray emission.

ISSN:0021-8979    

DOI:10.1063/1.336249

出版商:AIP    

年代:1985

数据来源: AIP