Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is – Heterojunction
Reexamination Certificate
1999-10-08
2002-10-29
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
Heterojunction
Reexamination Certificate
active
06472683
ABSTRACT:
FIELD OF INVENTION
This invention relates to quantum effect semiconductor devices and more particularly, to semiconductor quantum oscillation (Bloch oscillation) devices, which produce electromagnetic radiation in response to an applied electric field. The frequency of the electromagnetic radiation is between the highest microwave frequencies and the lowest infrared frequencies.
BACKGROUND OF INVENTION
The basic physical principle involved in the present invention is the dynamics of electrons in a crystal subjected to a uniform electric field. Sixty year ago, F. Bloch (F. Bloch, Z. Phys. 52, 555(1928)) and C. Zenner (C. Zenner, Proc. R. Soc. 145, 523 (1934)) have shown that an electron in a crystal could be described as a wave-packet composed of Bloch functions, and in the case where both scattering and interband tunneling into higher energy bands are absent, the electron will undergo periodic motion in k space in response to the applied electric field. The frequency of the periodic motion is eFa/h, where e is the electron charge, F is the electric field, a is the crystal constant, and h is the Plank constant. The oscillatory motion of an electron in k space is accompanied by a periodic motion in real space. This oscillatory motion of electrons in a crystal subjected to a uniform electric field is generally termed Bloch oscillation (or alternately Zenner oscillation, or Zenner-Bloch oscillation or Bloch-Zenner oscillation). Bloch oscillation is caused by the Bragg reflection of ballistically accelerated electrons at the Brillouin zone boundary, which leads to the periodic motion of electrons in the first Brillouin zone. The above description of electron motion is based on the dynamics of Bloch wave packet and is generally called a quasiclassical description. Subsequent theoretical work has shown that, an electron in a crystal subjected to a uniform electric field could also be described as a wave packet composed of quasibound Wannier-Stark states. In this fully quantum-mechanical description, Bloch oscillation appears as a special case of the quantum interference of Wannier-Stark states. For a detailed theoretical analysis of Bloch oscillation, the paper titled “Warrier-Stark Quantization and Bloch Oscillator” by G. Bastard and F. Ferreira could be consulted (in Spectroscopy of Semiconductor Microstructure, NATO ASI series, Plenum, N.Y., 1989, P.333). In order to realize Bloch oscillation, electrons should complete at least one oscillation period before being excited into higher energy bands (via interband tunneling sometimes called Zenner tunneling) or before experiencing scattering. For interband tunneling, when phonon effects are neglected, its upper boundary has been established at a rigorous level based on one-electron theory approximation, which shows that an electron may execute a number of Bloch oscillations before tunneling out of a band (A. Nenciu and G. Ninciu, J. Phys. A14, 2817(1981)). Therefore, interband tunneling should not be an obstacle to the realization of Bloch oscillation. As to scattering, there are two scattering mechanisms for electron in a solid, including phonon scattering and impurity scattering. Now, it is a common belief that due to the existence of scattering, Bloch oscillation should not be observable in conventional solid for all reasonable values of electric fields (G. von Plessen and P. Tomas, Phys. Rev. 45, 9185(1992)). P. Robin and M. W. Muller (J. Phys. C: Solid State Phys. 16, 4547(1983)) studied the properties of Bloch oscillation (called coherent Zenner oscillation in their paper) and found that only quasicohorent electrons can execute Bloch oscillation. Quasicohorent electrons are classical-like electron with minimized size x, and an oscillatory position expectation.
From an application standpoint, L. Esaki and R. Tsu proposed in their U.S. Pat. (No. 3,626,328) a Bloch oscillation device that employs a superlattice structure. The starting point for their proposed device is that the condition needed for Bloch oscillation should be more easily satisfied in superlattice structures. The argument is that a mini-Brillouin zone much smaller in width than the normal Brillouin zone is formed in the superlattice direction and as a result the scattering processes might be more favorable than in conventional solids. The objective of this invention is to provide a high-frequency semiconductor superlattice bulk oscillator based on the physical principle of Bloch oscillation. Up to now, the proposed device has never being realized (L. Esaki, in Science and Technology of Mesoscopic Structures, Springer-verlag, 1992, P.3). M. W. Muller, P. Robin and D. I. Rode (Workshop on Submicron devices Physics, ed. H. L. Grubin, (New York: plenum, 1983), P. 261) proposed a concept bulk semiconductor Bloch oscillation device. In this device, time-dependent intra-band tunneling of electrons from a narrow band-gap semiconductor into a wide band-gap semiconductor is suggested as the injection scheme. P. Robin and M. W. Muller (Semicond. Sci. Technol. 1, 218 (1986)) recognized that electrons must be injected in phase to realize Bloch oscillation. They also made a qualitative analysis on the scattering of Bloch oscillation (called Zenner oscillation in their paper) and pointed out that the polar scattering in a semiconductor such as GaAs could be tuned out if the frequency of Bloch oscillation is lager than the maximum longitudinal optical phonon frequency. In addition, they further realized that the primary difficulty with the Bloch oscillations (Zenner oscillations) in bulk semiconductors is to turn them on. Though all their above viewpoints regarding to realizing Bloch oscillation are correct and are very insightful, they came to a conclusion that one could not escape the high polar scattering rate during the electron injection phase. Their concept Bloch oscillation device does not become a working device. The reason is that the time-dependent tunneling electron injection scheme proposed in their device is not practical, and in addition this electron injection scheme could not escape the polar scattering. Therefore, the key to obtain practical Bloch oscillation becomes how to find a novel electron injection scheme, which could not only escape the polar scattering but also make the injected electrons in phase. Besides, the above semiconductor Bloch oscillation devices are concentrated on electrons in the conduction band, and little is reported on how to realize Bloch oscillation using the other type carriers, i.e. holes in the valence band.
SUMMARY OF THE INVENTION
It is among the objects of the present invention to provide a semiconductor Bloch oscillation device that employs a unique carrier injection scheme to inject carriers (including conduction band electrons and valence band holes). The carrier injection scheme provided will not only overcome the high polar scattering obstacle unresolved in prior art, but also inject both coherent electrons and coherent holes. In order to implement the above objectives, the present inventor made a broad and detailed study on the conditions required to realize Bloch oscillation and the following facts pertaining to Bloch oscillation are discovered:
1). Valence electrons in the full valence band of an intrinsic semiconductor experience much less scattering in comparison with conduction-band electrons and valence band electrons (represented as holes) in doped semiconductors. The argument is that, if these valence electrons experience phonon scattering, the only possible way of being scattered is into the conduction band, as there are no available states in the full valence band. And in reality, the probability of this kind of scattering is extremely small as the band gaps of common semiconductors are usually much larger than the energy of thermal phonons.
2). Under the action of a strong electric field, band-edge valence electrons (wave vector k nearly equal zero) of an intrinsic (unintentionally doped) semiconductor could be excited into the conduction band through the interband tunneling process, so it is possible to obtain fre
Chaudhuri Olik
Goltry Michael W.
Parsons Robert A.
Parsons & Goltry
Wille Douglas A.
LandOfFree
Semiconductor quantum oscillation device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor quantum oscillation device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor quantum oscillation device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2929225