Patent
1990-07-27
1991-07-23
Mintel, William
357 4, 357 19, 357 30, 357 90, 357 58, 350 9612, 350 9614, 350 9618, H01L 29161
Patent
active
050347837
ABSTRACT:
Polarization independence and higher intrinsic speed resulting from lowered device capacitance are achieved in a modulation-doped semiconductor heterostructure wherein a transfer barrier region including a graded bandgap semiconductor layer facilitates flow of carriers (electrons) from a doped reservoir to a narrow bandgap active region while an isolation barrier region confines carrier flow to be substantially within the graded bandgap region and the associated active region to minimize leakage current. The present modulation-doped heterostructure exhibits substantially equal end-boundary conditions in an unbiased condition for efficient cascading or stacking with additional modulation-doped heterostructures. Several embodiments of the present invention are described in which grading in the transfer barrier region is shown to include substantially continuous compositional grading, stepwise compositional grading, and superlattice grading. In these embodiments, the thickness of the active region is determined in proportion to the size of the optical effect which is to be produced.
REFERENCES:
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Drummond et al, "Quantum-Tailored Solid-State Devices", IEEE Spectrum, Jun. 1988, pp. 33-37.
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Zucker et al, "Large Refractive Index Changes in Tunable-Electron-Density InGaAs/InAlAs Quantum Wells," IEEE Photonics Technology Letters, vol. 2, No. 1, Jan. 1990, pp. 29-31.
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Chang Tao-Yuan
Zucker Jane E.
AT&T Bell Laboratories
Mintel William
Ranieri Gregory C.
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