Effects of Hydrostatic Pressure

Another important prediction of the BAC model is the characteristic anticrossing behavior of the E− and E+ transitions under applied pressure. The pressure dependence ofthe optical transitions associated with the E− and E+ subband edges in an In-free GaN0..015As0.985 sample and a Ga0.95In0.05N0.012As0.988. The anticrossing behavior of two strongly interacting energy levels with distinctly different pressure dependencies is unmistakably observed. The E− transition has a strong dependence at low pressures and gradually saturates at high pressures, whereas the E+ transition has weak pressure dependence at low pressures and displays a much stronger dependence at high pressures. The solid lines through the experimental data in the figure are results of calculations using Equation 2.9. The best fits to the data yield the energy of

the

nitrogen state, EN=EV+1.65 eV for both samples at atmospheric pressure, and it is independent of In concentration [26,41]. These results prove that the effects of alloying with In on the band gap can be separated from the shifts produced by the interaction with N states, allowing for an independent determination of EM from a given In concentration in Ga1−yInyNxAs1−x alloys. The observed change in the dependence of the E− and E+ transitions on pressure indicates that application of pressure gradually changes the character of the E− subband edge from extended EM-like to localized EN-like, and the character of the E+ subband edge from the localized-like to extended-like.

ROSSANA HERNANDEZ

Electrónica del estado solido

http://www.routledge.com/books/details/9781591690191/

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