| 摘要 |
PURPOSE:To change an effective band gap and reduce optical absorption on the edge face of an active layer, and to prevent the damage of the edge face by optical absorption by applying an electric field to the edge face of the active layer and bending a band. CONSTITUTION:Electrons and holes are injected to an active layer 1 from clad layers 2, 3 in order to oscillate an element. Electrons injected approximately exist on the lower side of the quasi-Fermi level Fc of a conduction band in the active layer 1, holes approximately exist on the upper side of the quasi- Fermi level Fv of a valence band, and a band is bent near an edge face when an electrode 5 is biassed at a positive value under the state. Consequently, electrons in the conduction band are increased on the edge face, holes in the valence band are decreased, and the energy of the light must be brought to energy Eg' or more where electrons in the uppermost section of the valence band can be excited at an energy level higher than the quasi-Fermi level of the conduction band in order to absorb light under the state. That is, an effective band gap is brought to the value Eg' larger than a band gap Eg on the inside, and light absorption near the edge face is reduced, thus preventing the damage of the edge face. |
