Electron Intersubband Transitions in N(+) Indium Gallium Arsenide Quantum Wells: Optical Selection Rules and Strain Effects
Abstract
This thesis presents an experimental and theoretical study of electron intersubband transitions in n ^+ InGaAs single quantum wells (SQWs). Using polarizationresolved techniques, we found electron intersubband transitions in n^+ InGaAs/AlAs SQWs exhibit two interesting features of (i) equally strong TE and TM absorption strength and (ii) strain dependent polarization splitting. A detailed account of 14 times 14 kcdotp perturbation theory and QW D_{2d} group symmetry analysis is given to explain these observations. In 14 times 14 kcdotp theory, interband mixing of QW subbands at k_  = 0, is strongly enhanced by the quantization effects. Highlying QW conduction subbands, therefore, have appreciated amount of Plike character due to band mixing effects. Interband coupling of Gamma_sp {15}{c}  Gamma_sp{15}{v} (Q), Gamma_sp{1} {c}  Gamma_sp {15}{v} (P _0), and Gamma_sp{1 }{c}  Gamma _sp{15}{c} (P _1) are found important in determining the intersubband selection rules and excitation strength. In particular, for crystals possessing spherical symmetry, Gamma_sp{15}{c}  Gamma_sp{15 }{v} coupling vanishes so that TEactive intersubband IR absorption is diminished and intersubband Raman scattering is abolished. Selection rules of intersubband IR absorption and Raman scattering can also be derived from QW D _{2d} point group symmetry analysis. A compressive QW biaxial strain causes a polarization splitting of intersubband transitions with TMactive transition occurred at the higher energy side of TEactive transition.
 Publication:

Ph.D. Thesis
 Pub Date:
 1994
 Bibcode:
 1994PhDT........83P
 Keywords:

 INDIUM GALLIUM ARSENIDE;
 Physics: Condensed Matter