摘要:

Transmission electron microscopy (TEM) and Raman scattering spectroscopy measurements were performed to investigate strain effects in lattice-mismatchedInxGa1−xAs/InyAl1−yAsmodulation-doped coupled double quantum wells. The high-resolution TEM images showed that a 100-ÅIn0.8Ga0.2Asdeep quantum well and a 100-ÅIn0.53Ga0.47Asshallow quantum well were separated by a 30-ÅIn0.25Ga0.75Asembedded potential barrier. The selected-area electron-diffraction pattern obtained from TEM measurements on theInxGa1−xAs/InyAl1−yAsdouble quantum well showed that theInxGa1−xAsactive layers were grown pseudomorphologically on the InP buffer layer. The values of the strain and the stress of theInxGa1−xAslayers were determined from the electron-diffraction pattern. Based on the TEM results, a possible crystal structure for theInxGa1−xAs/InyAl1−yAscoupled double quantum well is presented. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121723

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Ultrafast relaxation dynamics of light and heavy holes in GaAs following femtosecond valence-to-conduction-band excitation are measured by probing the light- and heavy-to-split-off hole transitions at different midinfrared wavelengths using the recently developed broadly tunable femtosecond optical parametric oscillator. The initial relaxation times are less than 75 fs, and a spectral hole-burning effect is seen. The results suggest that carrier–carrier and optical-phonon scattering, in particular, polar optical-phonon scattering, are the primary processes leading to the initial redistribution of heavy and light holes. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121724

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An investigation of the intermixing enhancement in an InGaAs/InGaAsP/InGaP partial laser structure following phosphorous implantation at 30, 80, and 7000 keV was carried out. We find that for the 30 and 80 keV implant energies, band gap shifts in excess of 80 meV could be imparted to a single embedded 8.5 nm InGaAs quantum well (QW) lying several thousand angstroms beyond the maximum ion range. As both the 30 and 80 keV implants kept the end of range damage spatially separate from optical mode region, the optical quality (inferred from photoluminescence intensity measurements) of the QW material was preserved to a greater extent than that resulting from the 7000 keV implants (where implant damage was directly created in the QW during ion bombardment). This result suggests that device structures containing InGaP cladding layers are well suited for monolithic integration as the masking of low energy ions with high lateral resolution can be achieved using routinely available masking techniques. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121725

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We derived expressions for the scattering rates due to dislocations in pseudomorphic heterostructures. We gave explicit formulas for those scattering rates in the free and the confined states, depending on the initial carrier energy and on the component of the total wave vector parallel to the dislocations. We demonstrated that this new scattering process could affect the electron mean velocity by more than 30&percent; from the ideal case treated commonly by the Monte Carlo simulators. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121726

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An ideal delta function or a Gaussian function has been assumed for the photoconductive switching response of a photoconductive sampling experiment. In this letter, an effective wave form reconstruction method, called minimum phase retrieval algorithm, is presented to find the correct response function of the photoconductive sampling gate. In addition, the method is applied to the retrieval of a picosecond guided pulse wave form obtained from an on-wafer photoconductive sampling experiment. The reconstruction method should be used for the terahertz wave form detection measurement, where the pulse width is comparable to the switching time of the sampling gate. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121727

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Etch rates of up to 2200 Å/min have been achieved on hexagonal silicon carbide (SiC) using dilute mixtures ofSF6:Arin a standard 13.56 MHz asymmetric parallel plate discharge. Furthermore, these etch rates have been realized with excellent pattern anisotropy profiles of approximately 1 at pressures in the range of 100–350 mTorr and theSF6fraction at or below 50&percent;. An understanding of the mechanisms responsible for the high etch rates in this simple, dilute, gas mixture can be achieved by considering the electrical characteristics of the radio frequency plasma. The conditions defining maximum etch rates are associated with peak fluorine ion and/or radical production, and can be defined entirely in terms of the relative current–voltage phase shift leading to optimal plasma impedance conditions and ultimately to maximal power deposition into the plasma. In addition, this study shows that the pervasive practice of utilizing oxygenated gas chemistries for SiC etching is not required, as previously thought, for carbon saturation and removal in order to obtain high etch rates, good surface morphology, and reliable pattern definition on SiC.

ISSN:0003-6951    

DOI:10.1063/1.121728

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We describe a method of Fermi energy measurement, based on the analysis of thermionic emission and diffusion over a barrier with a built-in charge. The method can be applied to a variety of semiconductors and has been successfully tested by measuring the Fermi energy in GaAs. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121729

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This letter reports an investigation of two unique dual inlaid metallization approaches with low pressure chemical vapor deposition (LPCVD) of aluminum (Al) for sub-0.35 &mgr;m ultra-large-scale-integration interconnect technology: (1) warm Al/CVD Al/coherent (coh.) PVD Al/coh. PVD Ti and (2) warm PVD Al/CVD Al/coh. PVD Ti or Al/selective CVD Al. The integration of thin coh. PVD Al, deposited with a physical collimator or a variation of ionized metal plasma technique, was found to be the unique and simple solution in providing void-free via and interconnect structures, which have not been reported elsewhere. Excellent electrical and electromigration results have been obtained. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121731

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

It is demonstrated that electric fields applied across phosphor layers strongly influence the cathodoluminescence emitted from these materials at low electron beam energies. The magnitude of these effects suggest that the primary mechanism may be alteration of the relative capture rates of electrons and holes at surface or near-surface defect sites associated with nonradiative energy losses. The sign of these effects in the two materials investigated suggests that the rate limiting step at low electric fields is the capture of electrons. Strong evidence for field-induced polarization and trapping of the beam-created electron-hole pair population is also presented. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121732

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report on a technique we have recently developed to fabricate very high quality gates and gated structures onInAs/AlxGa1−xSbquantum wells. The low thermal budget process leads to highly stable gates with extremely low leakage currents. Both electron and hole concentrations can be changed over a wide range by the application of modest gate voltages. We obtain adn/dVvalue of5×1011 cm2/Vfor electrons and1.6×1012 cm2/Vfor holes at 1.2 K. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121789

出版商:AIP    

年代:1998

数据来源: AIP