Electric‐field dependence of acceptor‐level binding energies in strained SiGe and InGaAs quantum‐well structures

The acceptor energies for strained SiGe (on Si) and InGaAs (on GaAs) quantum wells are calculated from a 4×4 k⋅p band structure that includes the effects of strain and electric fields. Both center‐ and edge‐doped cases are examined. The theory shows marked changes in the acceptor energies with both strain and electric field. The wide variation in binding energy for the edge‐doped quantum wells may provide a mechanism for tunable far‐infrared detectors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70960/2/JAPIAU-71-4-2023-1.pd

Effective constructions in plethysms and Weintraub's conjecture

We give a short proof of Weintraub's conjecture by constructing explicit highest weight vectors in the symmetric power of an even exterior power

Comparison of mode suppression and large signal modulation between lattice matched and strained InGaAs/AlGaAs quantum well lasers

Numerical techniques are developed to study the output spectra and to solve the coupled mode rate equations for InxGa1−xAs/Al0.3Ga0.7As quantum well lasers. The optical properties of the laser are calculated from a 4×4 k⋅p band structure which includes the effects of strain. We find that the side modes are severely suppressed in the strained laser. Large signal switching of the laser is also studied and the role of strain is identified in the device response. If the laser is switched from the off state to a state of given photon density in the lasing mode, then the strained system exhibits a faster time response. If, however, the laser is switched from the off state to a state of given total photon density, then the strained system has a slower time response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70732/2/APPLAB-59-19-2381-1.pd

Exercise apparatus

An apparatus and method for exercising whereby the user is supported by various mechanisms in such as way that the user's shoulder area is free to translate and rotate; the user's pelvic area is free to translate and rotate; or in any combination

The Effects of Day Care Participation on Parent-Infant Interaction at Home

This study assessed how parents who placed their children in a high-quality infant and toddler program were, over time, influenced by three salient features of the center: its child-centered focus, its social orientation, and its support for men in nurturing roles

The Effects of Day Care Participation on Parent-Infant Interaction at Home

This study assessed how parents who placed their children in a high-quality infant and toddler program were, over time, influenced by three salient features of the center: its child-centered focus, its social orientation, and its support for men in nurturing roles

Characterization of the Native Lysine Tyrosylquinone Cofactor in Lysyl Oxidase by Raman Spectroscopy

Lysine tyrosylquinone (LTQ) recently has been identified as the active site cofactor in lysyl oxidase by isolation and characterization of a derivatized active site peptide. Reported in this study is the first characterization of the underivatized cofactor in native lysyl oxidase by resonance Raman (RR) spectrometry. The spectrum is characterized by a unique set of vibrational modes in the 1200 to 1700 cm^(−1) region. We show that the RR spectrum of lysyl oxidase closely matches that of a synthetic LTQ model compound, 4-n-butylamino-5-ethyl-1,2-benzoquinone, in aqueous solutions but differs significantly from those of other topa quinone-containing amine oxidases under similar conditions. Furthermore, we have observed the same ^(18)O shift of the C=O stretch in both the lysyl oxidase enzyme and the LTQ cofactor model compound. The RR spectra of different model compounds and their D shifts give additional evidence for the protonation state of LTQ cofactor in the enzyme. The overall similarity of these spectra and their shifts shows that the lysyl oxidase cofactor and the model LTQ compound have the same structure and properties. These data provide strong and independent support for the new cofactor structure, unambiguously ruling out the possibility that the structure originally reported had been derived from a spurious side reaction during the derivatization of the protein and isolation of the active site peptide

Calculations of the electric field dependent far‐infrared absorption spectra in InAs/AlGaSb quantum wells

Excitonic and band‐to‐band absorption spectra are calculated for vertical incident radiation for the InAs/AlGaSb multiple quantum well structures. Due to the special band lineup of this heterostructure, the absorption spectra can be tailored to respond in far infrared. The electric field dependence of the spectra shows blue shift and enhanced absorption in contrast to the situation in type I quantum wells. Applications to far infrared detectors are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70612/2/APPLAB-55-9-888-1.pd

Refractive index and electro‐optic effect in compressive and tensile strained quantum wells

The effects of biaxial compressive and tensile strain on the excitonic resonances and associated changes in refractive index and electro‐optic effect in quantum wells have been calculated and measured. Theoretical calculations include the important heavy‐hole–light–hole band mixing effects. It is seen that the excitonic contributions dominate near the band edge. With increasing compressive strain the linear electro‐optic effect is slightly increased, while the quadratic effect is greatly enhanced. The effects are reversed in quantum wells under tensile strain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70690/2/JAPIAU-69-7-4071-1.pd

Effect of coherent strain on hydrogenic acceptor levels in InyGa1−yAs/AlxGa1−xAs quantum well structures

The biaxial strain produced in lattice‐mismatched epitaxy can have a substantial effect on the valence band structure. Theoretical results are presented for a hydrogenic acceptor in a quantum well under tensile and compressive strain. The acceptor level energy is a strong function of strain and could be used as a signature for the effect of strain on the valence band structure. Experimental studies are carried out on compressively strained InyGa1−yAs/ AlxGa1−xAs quantum well structures and the acceptor level energy is determined by photoluminescence measurements. Good agreement is found with the experiments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70617/2/APPLAB-57-2-180-1.pd