Browsing by Author "Tung, HH"

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A novel energy filter using semiconductor superlattices and its application to tunneling time calculations
(1996-12-01)
Tung, HH
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An artificial quantum-mechanical filter using superlattice structures is proposed in this paper, By gradually changing the barrier widths of a superlattice according to a Gaussian function, a broad-band and almost zero sidelobe transmission profile can be obtained. The WKB approximation is applied to demonstrate the phenomena of abrupt change of transmission profile, The proposed structure allows the incident electrons to be nearly totally transmitted when the impinging electron energy is in the passband, On the other hand, a complete reflection occurs when the impinging energy is in the stopband, By adjusting the structure parameters, the desired passband and stopband of such a filter can be obtained, Time evolution of an electron wavepacket moving through the structure is calculated by numerically solving the time-dependent Schrodinger equation, Numerical results clearly demonstrate the characteristics of total transmission and reflection, By simulating the movement of a totally transmitted wavepacket, ambiguity results from the nature of the wavepacket in the determination of electron tunneling time can be avoided. The generalized concept of matched quantum-mechanical wave impedance (QMWI) analogous to transmission line theory is presented to explaine the occurrence of total transmission of the proposed structure, The tunneling time (tau(QMWI)) calculated based on the concept of QMWI is compared with the accurate tunneling time obtained by our simulation.
A novel energy filter using semiconductor superlattices and its application to tunneling time calculations
(1996-12-01)
Tung, HH
;
Lee, CP
;
交大名義發表
;
電子工程學系及電子研究所
;
National Chiao Tung University
An artificial quantum-mechanical filter using superlattice structures is proposed in this paper, By gradually changing the barrier widths of a superlattice according to a Gaussian function, a broad-band and almost zero sidelobe transmission profile can be obtained. The WKB approximation is applied to demonstrate the phenomena of abrupt change of transmission profile, The proposed structure allows the incident electrons to be nearly totally transmitted when the impinging electron energy is in the passband, On the other hand, a complete reflection occurs when the impinging energy is in the stopband, By adjusting the structure parameters, the desired passband and stopband of such a filter can be obtained, Time evolution of an electron wavepacket moving through the structure is calculated by numerically solving the time-dependent Schrodinger equation, Numerical results clearly demonstrate the characteristics of total transmission and reflection, By simulating the movement of a totally transmitted wavepacket, ambiguity results from the nature of the wavepacket in the determination of electron tunneling time can be avoided. The generalized concept of matched quantum-mechanical wave impedance (QMWI) analogous to transmission line theory is presented to explaine the occurrence of total transmission of the proposed structure, The tunneling time (tau(QMWI)) calculated based on the concept of QMWI is compared with the accurate tunneling time obtained by our simulation.
An energy band-pass filter using superlattice structures
(1996-03-01)
Tung, HH
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel quantum mechanical energy band-pass filter (EBPF) using semiconductor superlattices is proposed. Such structures with a Gaussian superlattice potential profile allow the incident electrons to be nearly totally transmitted when the impinging electron energy is in the passband. On the other hand, a complete reflection occurs when the impinging energy is in the stopband, By adjusting the parameters of the potential profile and the superlattice, the desired passband and stopband of such filter can be obtained, Time evolution of an electron wave packet moving through such a structure is calculated by numerically solving the time-dependent Schrodinger equation. The numerical simulation clearly demonstrates the characteristics of total transmission and total reflection, The generalized concept of matched quantum-mechanical wave impedance (QMWI) analogous to that used in the transmission line theory is presented to explain the occurrence of total transmission of the proposed structures.
Design of a resonant-cavity-enhanced photodetector for high-speed applications
(1997-05-01)
Tung, HH
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We present a theoretical study of the effects of light field distribution on the frequency response of a resonant-cavity-enhanced p-i-n photodetector, Taking advantage of the flexibility of cavity design, one can tailor the light field distribution in the absorption region, Because of the difference in velocities of the carriers, the speed performances of the detector depend on the field distribution and the cavity design, The results of our work indicate that when the maximum of light field intensity happens near the p(+) edge of the depletion layer, the device shows the best speed performance, The frequency response, the impulse response, and the step response have been calculated for different structures to demonstrate the importance of the field distribution.