摘要:

An array of 3×4 ultrashallowp+–n++silicon junctions with gate (grid) structure has been developed for application as a micro‐vacuum triode. The device is fabricated by low energy ion implantation in conjunction with a new anode oxidation technique. The final junction depth is estimated to be 150 Å. Device structure and fabrication processes, especially on the formation and monitoring of the ultrashallow junction, are described. The current emission characteristics of the triode are investigated as a function of anode voltage, gate (grid) voltage, anode–emitter distance, and reverse bias current. The typical emission efficiency measured on bare silicon is 7.6×10−5.

ISSN:0734-211X    

DOI:10.1116/1.587206

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The electrical and optical properties of ZnO ultrafine particle (UFP) films prepared by a new dc gas discharge activated reactive deposition technique were investigated. IR spectra and work function were used to study the samples. The results show that ln σ vs 1000/Taccords with the Arrhenius equation at 227–300 °C, the absorption edge is near 480 nm, IR eigen absorption peaks of ZnO (UFP) films shift to high energy (short wavelength) with decreasing particle size. The work function changes with gas pressure was discussed.

ISSN:0734-211X    

DOI:10.1116/1.587207

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Nanometer scale oxide patterns were fabricated on titanium (Ti) surfaces on the basis of scanning tunneling microscope (STM) tip‐induced anodization. The spatial resolution of the method was limited to approximately 20 nm, owing to the surface roughness of the Ti film used. Chemical analyses of fabricated patterns by Auger electron spectroscopy proved that the surface chemical composition of the pattern was titanium dioxide (TiO2), and the oxide thickness on the pattern was certainly thicker than that of the native oxide on the unmodified area. A novel Ti‐metal resist process for nanolithography based on STM tip‐induced anodization was proposed. The Ti film on which anodized patterns were formed could be etched by hydrofluoric acid using the anodic oxide patterns as an etching mask. Ti lines of ∼60 nm in width were successfully fabricated by the present method.

ISSN:0734-211X    

DOI:10.1116/1.587208

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The electrostatic removal of lithium fluoride (LiF) from field‐emitter tips has been visualized at elevated temperatures in the transmission electron microscope (TEM). The apex of a field‐emitter tip coated with ∼1500 Å of LiF provides a unique substrate for observing the removal process in the TEM in real time, and its curvature generates the required electrostatic field strength. The influence of the imaging electron beam on coating morphology has been visually assessed. A LiF coating can tolerate an electron dose of ∼2000e−/Å2at room temperature without visible damage (at a resolution of 5 Å). At elevated temperatures a higher dose can be tolerated before visible damage is observed. Removal of LiF coatings at room temperature occurs at 18 MV/cm. At 800 °C piecewise removal of the coating occurs at 9 MV/cm. Synergistic effects of the electron beam and the electrostatic field on the removal of the coating were not observed. The removal of LiF at any temperature is attributed to field‐induced fatigue stress of the coating. Field desorption does not appear to play a significant role in the removal process. Implications for the production of ions from lithium fluoride thin films exposed to high electric fields (in laboratory experiments and in particle beam fusion accelerators such as PBFA II) are discussed.

ISSN:0734-211X    

DOI:10.1116/1.587209

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A novel ultrahigh vacuum (UHV) sample transfer system was constructed for the purpose of transferring Cl2‐gas etched GaAs samples from aninsituprocessing UHV multichamber to a scanning tunneling microscopy (STM) chamber. First, the performance of the sample transfer system was confirmed by an UHV‐STM observation of an As‐stabilized (2×4) structure of a molecular‐beam epitaxially (MBE) grown GaAs (001) surface. Next, four kinds of Cl2‐gas etched samples were prepared in the UHV multichamber, and an UHV‐STM observation of these etched surfaces was carried out. A strong dependence of the surface roughness on the etching temperature was observed; a 200 °C Cl2‐gas etched GaAs (001) surface exhibited a corrugation amplitude of several nanometers, which was about 1.5‐times smaller than that of a 70 °C etched surface. Through annealing under an arsenic pressure at 600 °C which is a typical temperature for MBE growth, the smoothness of the etched surfaces remarkably improved; the corrugation amplitude of the 70 °C etched surface decreased by a factor of 2, and that of the 200 °C etched surface decreased by a factor of 3–4. As a result, the 200 °C etched surface has become very smooth, being only about 1.5‐times rougher than the MBE grown surface. This indicates the usefulness of theinsitufabrication processes, since an interface formed by Cl2‐gas etching and following MBE regrowth has been guaranteed to be nearly as smooth as an as‐grown surface.

ISSN:0734-211X    

DOI:10.1116/1.587210

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A combined scanning tunneling microscopy/scanning tunneling spectroscopy (STS) system has been developed by which the spatially resolved electronic structure of a surface can be measured step by step consecutively. With this system, etched GaAs(100) surfaces have been studied in ambient with experimental measurements of the (d ln I/d ln V) vsVcurves along a line on the surfaces. The curves exhibit the basic band structure of GaAs. Specific band energies from the curves are plotted versus the surface position at which each of the corresponding STS spectra is measured. The plots show a correlative variation of the surface electronic structure with the surface corrugations. The results present the possibility of investigating the spatial variation of the surface electronic states with surface structures. Based on the correlative variation of the surface electronic structure, a way of imaging the surface corrugation more sensitively is proposed.

ISSN:0734-211X    

DOI:10.1116/1.587211

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

We used two‐step molecular beam epitaxial (MBE) growth to integrate monolithically single and double vertical‐cavity structures on a wafer. This technique is useful for making a single vertical‐cavity surface‐emitting laser–thyristor with a low threshold and a double vertical‐cavity heterojunction phototransistor with both a high responsivity and a large spectral bandwidth. Regrowth on a patterned distributed Bragg reflector after thermal desorption of a passivating GaAs layer resulted in the laser in the single‐cavity section having a threshold current density of 1.0 kA/cm2, which is comparable to that of one grown by conventional one‐step MBE. Controlling thickness to within ±0.3% resulted in the regrown double‐cavity section having a bandwidth of 5 nm.

ISSN:0734-211X    

DOI:10.1116/1.587212

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Molecular beam epitaxy grown AlInAs/GaInAs single quantum well high electron mobility transistor structures (SQW‐HEMT) on InP were developed for transistor applications with high current drive capability. Use of low growth temperatures for the layers below the GaInAs channel in case of the inverted interface proved to be essential to achieve simultaneously high electron concentrations in the channel region and mobilities equal to those of normal single heterojunction HEMT structures. The mobilities obtained in SQW‐HEMT structures which employed Si δ‐doping on both sides of the SQW channel were found to be only weakly dependent on the channel thickness down to 16 nm whereas below the mobility tended to degrade. Based on theoretical calculations an optimum spatial distribution of the carriers is deduced aiming at high channel electron density and low parallel concentration in the lower supply region by optimizing the thickness of the spacers and the asymmetric distribution of the donors above and below the channel. Further improvements of the SQW‐HEMT structures were obtained by incorporating elastically strained In‐rich channels. In this way, increased mobilities and concomitantly enhanced electron concentrations have been achieved. Unsurpassed 77 K mobilities amounting up to 55.000 cm2/V s in conjunction with a Hall carrier density of 6.0×1012cm−2, which compares with a simulated channel density of 5.4×1012cm−2, were attained. 0.6 μm gate length devices fabricated on the optimized SQW‐HEMT layer structures clearly demonstrate the superior performance of the SQW design in terms of saturation current without compromising the pinch‐off behavior.

ISSN:0734-211X    

DOI:10.1116/1.587213

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Self‐aligned processing of high efficiency power heterojunction bipolar transistors (HBTs) using implant isolation, selective wet and dry etching for mesa formation, plasma‐enhanced chemical vapor deposited SiNxfor sidewall spacers and through‐wafer via connections is reported. GaAs/AlGaAs and GaAs/InGaP HBTs grown by metalorganic molecular beam epitaxy utilizing carbon for high, well‐confined base doping produced power‐added efficiencies of 63%, power gain of 10 dB and output power of 1.7 W at 4 GHz for twelve 2×15 μm2double‐emitter finger devices (GaAs/AlGaAs) and 57% power‐added efficiency, power gain of 11.3 dB and output power of 0.6 W at 4 GHz (GaAs/InGaP), respectively.

ISSN:0734-211X    

DOI:10.1116/1.587537

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A dry‐etching process that produces very smooth facets in the AlGaAs/GaAs material system is described. Chemically assisted ion beam etching (CAIBE) is used to fabricate the facets, with SiO2as the etch‐mask. Reactive ion etching (RIE) is used to transfer the resist pattern to the underlying SiO2layer. RIE operating conditions, including gas type, power density, and etching pressure were characterized to achieve smooth SiO2sidewalls. It is found that CF4etching at low power density of 0.10 W/cm2and low pressure of 1 mTorr produces very smooth SiO2sidewalls. As a result, excellent etched facets are obtained by CAIBE, using SiO2as the etch‐mask. This dry‐etching process is being used to fabricate waveguide diode ring lasers. A self‐aligned etching process, which defines both the ridge and the facets for the ring lasers in the same lithography step, is also discussed.

ISSN:0734-211X    

DOI:10.1116/1.587538

出版商:American Vacuum Society    

年代:1994

数据来源: AIP