摘要:

This article discusses the etching and selectivity of 3C-SiC films grown on Si substrates usingCHF3/O2andCHF3/O2/He plasmas at a pressure of 1.75 Torr. The addition of helium increases the etch rates of SiC and Si for most CHF3and O2concentrations. For both CHF3/O2and CHF3/O2/He plasmas with O2concentrations up to 85%, the SiC etch rate increases monotonically and the Si etch rate decreases monotonically with increased percentages of O2. At an O2concentration of 80%, the addition of helium to the CHF3/O2plasma results in an etch rate of 1267 Å/min, which is the highest reported for etching 3C-SiC using a CHF3-based plasma in a conventional, parallel plate plasma reactor. The addition of helium also increases the etch anisotropy. This study also investigated aluminum micromasking of SiC etch fields and finds the primary source to be sputtered aluminum from the etch mask.

ISSN:1071-1023    

DOI:10.1116/1.589858

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Two methods for maskless patterning of SiC using a focusedGa+beam are demonstrated: the enhancement of the chemical etching rate by amorphization of c-SiC to a-SiC and physical sputtering if deep structures are required. Both methods are followed by wet chemical etching inHF:HNO3=1:1 at 80 °C to remove the remaining a-SiC. Assuming the critical displacement density for amorphization to be about the same as for the onset of etching, the measured depths of the structures were compared with the depths of amorphization estimated withTRIM 87calculations. To find optimum sputtering parameters the energy dependence of the sputter yield was investigated and compared withTRIM 87simulations, too. Damage after implantation and after wet chemical etching was investigated by means of Raman spectroscopy. No damaged material remaining after wet chemical etching could be detected.

ISSN:1071-1023    

DOI:10.1116/1.589859

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Dense, periodic arrays of holes and troughs have been fabricated in silicon, silicon nitride, and germanium. The holes are approximately 20 nanometers (nm) wide, 20 nm deep, spaced 40 nm apart, and uniformly patterned with 3×1012holes on a three inch wafer. To access this length scale, self-assembling resists were synthesized to produce either a layer of hexagonally ordered polyisoprene (PI) spheres or parallel cylinders of polybutadiene (PB) in a polystyrene (PS) matrix. The PI spheres or PB cylinders were then degraded and removed with ozone to produce a PS mask for pattern transfer by fluorine-based reactive ion etching. A PS mask of spherical voids was used to fabricate a lattice of holes and a mask of cylindrical voids was used to produce parallel troughs. This technique accesses a length scale difficult to produce by conventional lithography and opens a route for the patterning of surfaces via self-assembly.

ISSN:1071-1023    

DOI:10.1116/1.589860

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A comparison of notching of metal etching inCl2/BCl3and HCl plasma was made by using a transformer coupled plasma etcher. We found that notches can be reduced by eliminatingBCl3from gases for overetching. Furthermore, the HCl/He overetch process provides notch-free profiles with high selectivities. The reduction in sidewall attack by heavy ions (e.g.,BCl2+orBCl3+) and scavenging of excess Cl radicals by the H radical are considered possible reasons for reduced notching in the HCl/He process.

ISSN:1071-1023    

DOI:10.1116/1.589861

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Etching results using the solution system of citric acid/H2O2and de-ionizedH2O/buffered oxide etch are shown to provide good selective wet etching of AlGaAs/GaAs structures. ForAlxGa1−xAs(x0.7) quickly decreases with decreasing Al composition in de-ionizedH2O/buffered oxide etch solution, providing a high degree of etching selectivity. These simple selective etching processes have been applied to define AlAs/GaAs distributed Bragg reflector mesas in a vertical-cavity surface-emitting laser structure.

ISSN:1071-1023    

DOI:10.1116/1.589862

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We report on the realization of via holes on InP material (for the first time to our knowledge) using bromine/methanol wet chemical etching. Typical dimension of the via holes is about 80μm in diameter. A specific layout has been accomplished to obtain the via hole equivalent circuit. Measurements have been performed from 50 MHz to 30 GHz. They exhibit losses of 0.1 dB at 30 GHz. The via hole equivalent circuit is found to be a resistance and an inductance in serial configuration with typical values of 0.4Ωand 26 pH, respectively.

ISSN:1071-1023    

DOI:10.1116/1.589863

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

InGaAlAs epilayers lattice matched to an InP substrate are grown by molecular beam epitaxy with band gap energies varying in the range 0.8–1.42 eV. TheI–V/C–Vcharacteristics of the Schottky diodes fabricated on InGaAlAs/InP heterostructures are investigated in the temperature range 80–300 K to study the variation of barrier heights with the Al mole fraction in the alloy. It is noted that at room temperature due to the dominance of thermionic emission the Schottky characteristics are not observable on low Al fraction structures, primarily because of the low metal–semiconductor barrier and low heterostructure barrier potentials. However, at 80 K the potentials are high enough to provide measurable characteristics. For an Al mole fraction of 0.23, the band lineup of the InGaAlAs/InP heterostructure changes from type I to staggered type II. Also, for the band gap engineered InGaAlAs alloys, the variations of mobility and doping concentration in the temperature range 80–400 K are presented as a function of the Al mole fraction in the alloy.

ISSN:1071-1023    

DOI:10.1116/1.589864

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Photoreflectance (PR) spectra of GaAs/AlGaAs multiple quantum well waveguides at room temperature were investigated. In addition to the allowed and symmetry forbidden transitions between confined states, a number of transitions involving the unconfined states were also observed. The coupling between the multiple wells (miniband dispersion) of both confined states and unconfined states (above barrier band gap) were reported. By using the propagation-matrix method, the energies for both confined transitions and unconfined transitions were calculated and shown to agree with the experimental values determined by fitting the PR spectra to the theoretical line shape expression.

ISSN:1071-1023    

DOI:10.1116/1.589865

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

TwentyGaAs/Al0.3Ga0.7As tilted T-shaped quantum wires (T-QWRs) on a (111)B facet were uniformly fabricated with a two-step growth of molecular beam epitaxy (MBE), which consists of a glancing-angle MBE ofGaAs/Al0.3Ga0.7As multi-quantum well layer with 20 GaAs wells (a well width ofLw=6.1 nm) on reverse-mesa stripes on a (001) GaAs substrate and MBE overgrowth of aGaAs/Al0.3Ga0.7Assingle-quantum well withLw=6.3 nmon a (111)B facet. Full width at half maximum of a photoluminescence peak(λ=792 nm)from the tilted T-QWRs was as small as 8.7 meV at 28 K, which is comparable with those (6 meV,Reference 5 10 meVReference 10) of conventionalGaAs/Al0.3Ga0.7As T-QWRs (6.8 nm/5.8 nm, 7 nm/7 nm) fabricated by the cleaved-edge overgrowth.

ISSN:1071-1023    

DOI:10.1116/1.589866

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Continuous wave and time-resolved photoluminescence (PL) measurements were performed in order to understand the temperature and power dependence of the luminescence from visible quantum dots (QDs). The PL decay rate is found to be independent of temperature up to 100 K, confirming the high quality of the QDs. However, the intensity of the luminescence decays rapidly, which proved to be due to nonradiative recombination in the barriers, preventing the carriers from reaching the QDs. The dependence of the decay rate on incident power was also studied at 4.2 K. Excited state emission was seen at this temperature.

ISSN:1071-1023    

DOI:10.1116/1.589932

出版商:American Vacuum Society    

年代:1998

数据来源: AIP