摘要:

For the design ofSi1−xGexoptical waveguide devices, one of the most important material parameters is the refractive index difference,δn,between the alloy layer and the silicon substrate. We have measuredδnfor pseudomorphic waveguide layers with germanium fractions between 1% and 9% by fitting measured mode profiles to theoretical mode shapes for a wavelength of 1.3 μm. For transverse electric modes, the measuredδnvaried with composition asδn=(0.34±0.05)x.Transverse magnetic modes were more tightly confined to the waveguide layer and the index was determined to beδn=(0.55±0.05)x.The large difference between the two polarizations results from strain-induced birefringence. Bulk photoelastic theory, using constants appropriate for pure silicon, predicts strain contributions to the index of−0.080xand+0.095xfor light polarized parallel and perpendicular, respectively, to the substrate plane, consistent with experimental observations.

ISSN:1071-1023    

DOI:10.1116/1.590088

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The thermal stability of high quality, strainedSi1−xSnx,2.5%⩽x⩽5%,grown by molecular beam epitaxy on Si 〈001〉 substrates has been investigated by Rutherford backscattering spectrometry and transmission electron microscopy. As a result of annealing at temperatures in the range 400–950 °C for 1 h, both relaxation by precipitation of Sn and generation of misfit dislocations and dislocation loops were found, consistent with the low solubility of Sn in Si and the large lattice mismatch between Si andSi1−xSnx.In the epitaxial, strainedSi1−xSnxlayers, where the strain is proportional to the Sn concentration, the threshold temperature for generation of precipitates and misfit dislocations was found to decrease with increasing Sn concentration. Above the threshold temperature the influences of the different relaxation channels change considerably with temperature and composition; an orthogonal interfacial misfit dislocation network is seen at temperatures close to threshold while at higher temperatures mainly dislocations in the bulk are found coexisting with large precipitates. The compositional metastability that leads to the precipitation process, reduces the Sn concentration in the matrix, however, neither this depletion of Sn from the matrix ofSi1−xSnxnor the relaxation due to misfit dislocations cause a fully relaxation of theSi1−xSnxlayers.

ISSN:1071-1023    

DOI:10.1116/1.590089

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Scanning tunneling microscopy has been used to study the surface morphology of strainedIn1−xGaxAslayers (either 2% compressively or 2% tensilely strained forx=0.18orx=0.75,respectively) grown by molecular beam epitaxy on (001) InP substrate under cation-stabilized conditions. Under such growing conditions a smooth two-dimensional (2D) surface morphology is well preserved until the onset of plastic relaxation. This behavior is completely unlike the 2D/3D growth mode transition observed under As-stabilized conditions of growth. Along with the 2D growth mode stabilization, a step-edge smoothing is also observed. These results are assigned to a high value of step formation free energy on (4×2) reconstructed surfaces. The resultant increase in surface tension delays the onset of coherent 3D island formation beyond the onset of plastic relaxation and stabilizes 2D growth.

ISSN:1071-1023    

DOI:10.1116/1.590090

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Reflectance modulation thermography has been used to determine facet temperatures of InGaAs/GaAs double quantum well (QW) GRINSCH ridge-waveguide lasers possessing band gap shifted extended cavities (BSECs). The incorporation of BSECs produced by mega-electron-volt ion-implantation enhanced QW intermixing, significantly decreased the laser facet temperatures and should result in increased device longevity prior to the onset of catastrophic mirror failure. Low energy implants in Al-free InGaAs/InGaAsP/InGaP laser structures exhibited large effective diffusivities of intermixing enhancing defects from the implant damage regions. This latter material system is particularly well suited for the implementation of BSECs as end of range damage from the implant can be kept spatially isolated from the optical mode regions.

ISSN:1071-1023    

DOI:10.1116/1.590230

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The existence of localized states at InSb-like interfaces of AlSb/InAs superlattices is predicted using empirical pseudopotential calculations. These predictions are shown to be in agreement with those ofab initiopseudopotential calculations performed using the local density approximation of density functional theory, demonstrating the ability of the empirical approach to describe the microscopic features of the interface. The frequency dependence of the absorption coefficient is calculated for a series of AlSb/InAs superlattices with differing interface configurations, and the role of the interface localization in determining the optical response is identified.

ISSN:1071-1023    

DOI:10.1116/1.590232

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Phosphorus incorporation during chemical beam epitaxial (CBE) growth ofGaAs1−xPxfrom triethylgallium, tertiarybutylarsine, and tertiarybutylphosphine is investigated. Reflection high-energy electron diffraction intensity oscillations are used to measure the phosphorus incorporation during the As-limited and the (As+P)-limited growth on a Ga-rich surface. The resulting phosphorus mole fraction is compared with the phosphorus composition measured by x-ray rocking curves on the strainedGaAs1−xPxlayers grown by conventional CBE with a simultaneous supply of group V and group III elements. The phosphorus incorporation rate during CBE growth is lower than that measured during the group V controlled growth but is still much higher than the incorporation rate reported for molecular beam epitaxy growth using elemental sources.

ISSN:1071-1023    

DOI:10.1116/1.590091

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The photoresponse ofIn0.5Ga0.5Asmetal–semiconductor–metal photodetectors is related to the presence of a hole trap. Detectors made from material grown with anIn0.5Al0.5Asbuffer layer had no measurable trap density when examined using deep-level transient spectroscopy, and the full width half maximum (FWHM) of the photoresponse was 80 ps at 5 V bias for 3 μm interdigitated fingers and spacings. Detectors made from material grown without anIn0.5Al0.5Asbuffer layer had a hole trap and a FWHM photoresponse of 220 ps. This deep hole trap is likely related to impurities that diffused upward from an interface of an InP substrate and an InGaAs epilayer.

ISSN:1071-1023    

DOI:10.1116/1.590233

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The use of forward biasing the source-substrate junction in metal–oxide–semiconductor transistors, to reduce its threshold voltage is a simple method to realize low power complementary metal–oxide–semiconductor integrated circuits. A 2 μm longn-metal–oxide–semiconductor field effect transistor was used as the device under test. The threshold voltage was measured in the temperature range of 300–77 K, using two different methods. The classic long channel threshold voltage model was fitted by optimization to the experimental data of the reverse-biased substrate, and the model with the fitted parameters was used to calculate the threshold voltage under forward-biased substrate conditions. The agreement between the fitted and extrapolated threshold voltage with the experimental values demonstrated the validity of this classic model for a substrate forward bias up to 0.5 V, and for a wide temperature range.

ISSN:1071-1023    

DOI:10.1116/1.590092

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The damage introduced into an InGaAs/InGaAsP quantum well structure duringCH4/H2reactive ion etching (RIE) processes was measured, for plasma powers from 20 to 100 W, using low temperature photoluminescence. The damage depth profile is estimated to be around 12–70 nm after annealing at500 °Cfor 60 s using a rapid thermal annealer. A reduced damage RIE process has been developed to fabricate InGaAs/InGaAsP multiquantum well ridge waveguide lasers. The performance of these lasers has been compared to that of lasers fabricated from the same epilayer using wet etching to form the ridge. The resultant threshold currents were essentially indistinguishable, being 44.5 and 43 mA, respectively, for dry and wet etched lasers with500 μmlong laser cavities.

ISSN:1071-1023    

DOI:10.1116/1.590093

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The plasma–surface interaction duringCH4–H2reactive ion etching processing of InP is described in detail by means of plasmadiagnostics (optical emission spectroscopy and mass spectrometry) and x-ray photoelectronspectroscopy (XPS) surfaceanalysis. The influence of the input power is carried out for differentCH4–H2mixtures in terms of InP etch rate,etch product andCH3radical detection and surface damage characterization. In particular detailed XPS results allow the study of the changes in the stoichiometry andamorphization of the surface with the input power. In addition, for a given power, the quality of the etched surface improves by increasing the fraction of methane in the gas mixture. Asan example, the best surface stoichiometry(InP0.86)is obtained for a pure methane plasma running ata high power (300 W). In general, it is shown that the lower the P depletion, the lower the amorphization, which is indicative of a general improvement of the etched surface quality.Based on the XPS results, a three-layer model is proposed for the representation of the surface in thecourse of etching. The damaged layer situated over the bulk InP is composed of a superficial P-depleted layer and of a stoichiometric amorphized InP layer. Using thecurve-fitting of theP 2pspectra, the thickness of the different layers is estimated. As an example, a damaged layer as low as 37 Å thick is obtained for puremethane plasma at 15 mTorrand a power of 300 W, whereas our standard conditions (10%CH4–H2,50 mTorr, and 80 W) give a damaged layer of 90 Å. The experimental observations give evidence of the need for both ion bombardment and activeneutral species to obtain etching. The improvement of the etch process is then explained by an improved In removal rate which is actually the limiting step in theetching mechanism of InP.

ISSN:1071-1023    

DOI:10.1116/1.590213

出版商:American Vacuum Society    

年代:1998

数据来源: AIP