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Quantum well intersubband transition detection and modulation


Xu, Yuanjian (1997) Quantum well intersubband transition detection and modulation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/pbpa-dx11.


This thesis is a theoretical and experimental investigation of the intersubband transitions in quantum well structures. The I-V characteristics, infrared absorption spectra, and photoresponse spectra of superlattices are used to characterize multiple quantum well structure properties in unipolar devices. An important numerical method for solving the problem of bound-to-continuum transitions, the transfer matrix method, is presented for the self-consistent calculations. Although the boundary conditions are relaxed due to the calculation self-consistentcy, inappropriate boundary conditions were previously included in the literature. The first observation of the quantum interference effect in the photocurrent spectra is described using a weakly coupled bound-to-continuum transition quantum well structure and electric field domain formation in the device. This effect persists even at high biases where Kronig-Penny minibands of periodic superlattice potential in the continuum are destroyed. Using this observation, the electric field domain formation and the electron coherence length in superlattices were analyzed. A large off-resonant energy level alignment between two neighboring wells in the high field domain was observed. The effect of temperature on the transport properties was also discussed. As a further study of electric field domain formation in superlattices, an optical experiment using Stark effect is suggested. The dependence of the absorption spectral linewidth of quantum well intersubband transitions on the electron population in the well is experimentally demonstrated using field-induced charge transfer and thermal-induced charge transfer in an asymmetric coupled quantum well structure. We show that this population-induced broadening is very important in the broadening of intersubband transitions in quantum well structures and that previously reported linewidth values for the contribution from donor scattering were overestimated. Many body effects and single-particle band non-parabolicity are the likely causes. An electronic light chopper based on population modulation was fabricated using the asymmetric coupled quantum well structure. A modulation depth of 45% has been demonstrated using 50 periods of the coupled well structure.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Quantum well intersubband transition
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Yariv, Amnon
Thesis Committee:
  • Unknown, Unknown
Defense Date:24 October 1996
Record Number:CaltechETD:etd-05112005-153655
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1723
Deposited By: Imported from ETD-db
Deposited On:11 May 2005
Last Modified:16 Apr 2021 22:54

Thesis Files

PDF (Xu_y_1997.pdf) - Final Version
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