摘要:

Electroreflectance (ER), and its contactless form photoreflectance (PR), are optical characterization techniques that can be used to directly measure the surface electric field, and hence, the surface Fermi level, of GaAs films via the Franz–Keldysh effect and the Schottky relation. Photoreflectance was used to measure the surface electric field of an as‐grown Si‐doped GaAs film before and after exposure to a photochemical wash of low‐conductivity water or an Na2S ⋅ 9H2O treatment at 295 K. As reported recently by various authors, these treatments are claimed to reduce the GaAs surface state density and unpin the surface Fermi level. Calibration ER experiments were performed on a separaten‐GaAs Ni Schottky barrier and found barrier heights of about 0.80 eV at 82 and 295 K. For the calibration sample, the surface Fermi level of an air exposed surface was determined to be 0.73 eV below the conduction band at 295 K based on the PR measurements. For the as‐grown films, after treatment, the surface Fermi levels were found to be about 0.63 eV. The measurements imply that the treatments affect a minority of the surface states and leave the surface Fermi level essentially pinned. Furthermore, these states have a large influence on the photoluminescence intensity and surface recombination velocity of the GaAs surface. The results of the treatments are not inconsistent with the unified defect model.

ISSN:0734-211X    

DOI:10.1116/1.584202

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The microstructure of an Al–Ge–Ni Ohmic contact top‐type GaAs has been investigated by cross‐sectional high resolution and analytical electron microscopy. The contact is found to consist of a continuous polycrystalline layer of Al3Ni adjacent to the GaAs with single crystals of the same phase and larger Ge rich structures on the surface. The contact interface is extremely planar and uniform with intrusive phases in the GaAs entirely absent. The possible reasons for this and the observed Ohmicity of the contact are discussed.

ISSN:0734-211X    

DOI:10.1116/1.584203

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The adsorption of cesium ions from aqueous sulphide solutions on semiconductors belonging to the II–VI family of compounds was investigated using Rutherford backscattering in the random and channeling direction, and proton‐induced x‐ray emission, with computer simulation of the spectra. Whereas CdSe and CdS are stable against surface exhange (in the dark) ZnSe is unstable in such solutions and extensive O/Se and S/Se exchange occurs after relatively short periods of immersion. Furthermore, while cesium ions are chemisorbed mostly on the semiconductor surface of CdSe and CdS with some penetration into the crystal matrix, extensive indiffusion of cesium occurs in ZnSe. These results may explain the difference in the behavior of these two kinds of materials in sulphide electrolyte under illumination. They can also explain the fact that in ZnSe the work function of the semiconductor does not vary appreciably upon immersion in cesium containing solution while for CdSe and CdS the work function decreases by 150–200 mV and consequently the open circuit potential increases by that amount in cesium sulphide solutions.

ISSN:0734-211X    

DOI:10.1116/1.584204

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

An inverse Laplace transform method has been used to extract composition depth profiles from angle‐resolved x‐ray photoelectron spectroscopy data from oxidized Si and Ar+bombarded GaAs. An iterative procedure determines a least‐squares curve fit of the data using the Laplace transforms of step functions, which are summed to yield the composition profiles. For a sample of native oxide on a Si wafer, the composition profile defines the thickness and chemical layering of the various silicon oxide states. For GaAs sputtered with 1.5‐, 3.0‐, and 5.0‐keV Ar+, the composition depth profiles show a surface composition near the bulk ratio, a subsurface As depletion, the extent of which increases with increasing ion energy, then a return to the bulk composition at greater depth. These As composition profiles result from preferential sputtering caused by surface segregation enhanced by sputter‐assisted diffusion in the near surface region.

ISSN:0734-211X    

DOI:10.1116/1.584205

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Tantalum was sputter deposited on (111) Si substrate under low‐energy ion bombardment in order to study the effects of the ion energy on the silicon transport into the Ta layer. The Si substrate was heated up to 500 °C during growth. For ion energies up to 180 eV silicon is not transported into tantalum and the growth temperature has no effect. An ion bombardment energy of 280 eV enhances the transport of silicon throughout the tantalum layer. Growth temperatures up to 300 °C have no effect on the silicon transport which is mainly enhanced by the ion bombardment. For growth temperatures between 300 and 500 °C, the silicon transport is also enhanced by the thermal diffusion. The experimental depth distribution of silicon is similar to the theoretical depth distribution calculated for the case of an interdiffusion. The ion‐enhanced process of silicon transport is characterized by an activation energy of 0.4 eV. Silicon into the layers as‐grown at 500 °C is in both states, amorphous silicide and microcrystalline cubic silicon.

ISSN:0734-211X    

DOI:10.1116/1.584206

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

This paper evaluates reactively sputtered WSiN films as an annealing cap for GaAs substrate. WSiN film successfully suppresses As and Ga outdiffusion. The WSiN/SiO2/SiN/substrate multilayer annealing cap reconfirms this. As and Ga accumulate in the WSiN/SiO2interface after annealing at 800 °C for 20 min. The accumulated As peak concentration is estimated to be 1019atoms/cm3. X‐ray diffraction shows WSiN film remains in an amorphous phase, exhibiting no recrystallized grain boundary. Film stress only changes by one‐half before and after annealing. These characteristics are very different from other refractory metals such as WN and WSi which change from amorphous to crystalline phase after annealing. It is therefore concluded that reactively sputtered WSiN films prevent As and Ga outdiffusion and form a good annealing cap for GaAs.

ISSN:0734-211X    

DOI:10.1116/1.584207

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A new formation process of anodizable structures ofn,n+, andn−silicon for the production of silicon‐on‐insulator (SOI) structures is described. In this process, proton implantation is employed to produce a high donor concentration layer near the surface ofn‐type silicon substrates, and nitrogen ion implantation is employed to define highly resistive islands in the high donor concentration layer. The anodization of silicon in HF solution to form porous silicon and the consequent oxidization of the porous silicon to form silicon dioxide is restricted to the high donor concentration regions. It is demonstrated that silicon islands with a width of 50 μm and a thickness of 0.55 μm are successfully isolated by an oxidized‐porous‐silicon layer with a thickness of 2.25 μm.

ISSN:0734-211X    

DOI:10.1116/1.584208

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A nondestructive, noncontact, optical method was successfully developed to measure thicknesses of titanium and titanium silicide thin films by observing infrared transmissions. These transmissions can be substantial for film thicknesses of up to 850 Å in titanium and 1000 Å in titanium silicide. The technique provides a convenient and reliable means for in‐line process monitoring of a Ti‐salicide (titanium self‐aligned silicide) process module for gate, source, and drain formation in integrated circuits. A linear relationship between absorbance and film thickness was obtained for titanium and titanium silicide films. This behavior can be explained very well by the classical wave propagation theory of metallic films.

ISSN:0734-211X    

DOI:10.1116/1.584209

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Four methods for fabricating polysilicon contacted bipolar junction transistors (BJT’s) have been investigated. In the first method polysilicon was deposited using low‐pressure chemical vapor deposition (LPCVD) at 620 °C. In the remaining three methodsa‐Si was first deposited and then recrystallized to form polysilicon. In the second methoda‐Si was deposited using LPCVD at 580 °C. The third method used plasma‐enhanced chemical vapor deposition (PECVD) to deposita‐Si:H. The fourth method involved a plasma etch with argon or hydrogen prior to deposition ofa‐Si:H using PECVD. The results indicated that using the PECVD method for depositinga‐Si:H without any prior plasma‐etch step and recrystallizing it to form polysilicon resulted in the highest current gain (β) enhancement of 3.5 and also allowed the reduction of the polysilicon anneal temperature down to 800 or 900 °C from 1000 °C. The compactness in the spread of the peak β values for the devices fabricated using this technique also reflects its ability for reproducible fabrication of polysilicon contacted shallow emitter BJT’s.

ISSN:0734-211X    

DOI:10.1116/1.584210

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A simplified model is developed for localized ion beam induced metal deposition from metal‐containing gases. The model takes into account simultaneous deposition and resputtering of deposited material and is based on two parameters, i.e., deposition cross section and sputtering yield of the deposit. Numerical values of these parameters are determined from experimental measurements of layer thickness under different deposition conditions for the case of deposition of Al‐containing layers by 3.5–10 keV Ar bombardment in a trimethyl‐aluminum (TMA) atmosphere. The knowledge of these parameter values allows one to predict deposition rates for given experimental conditions (current density, gas pressure, and beam energy).

ISSN:0734-211X    

DOI:10.1116/1.584211

出版商:American Vacuum Society    

年代:1988

数据来源: AIP