| 摘要 |
PROBLEM TO BE SOLVED: To make a driving voltage lower and to embody a high extinction ratio by adopting such a structure which negates a built-in electric field for the potential structure of quantum wells. SOLUTION: This modulator has the structure that the electron affinity in the one well layer increases toward a p-side and the energy at the top end of a valence band decreases toward then p-side. In this structure, the increase of the band discontinuous quantity of electrons may be nearly equal to 45meV and the decrease of the band discontinuous quantity of holes to 41meV. In other words, the linear changing of the band discontinuous quantity of the conductor band (electrons) and the valence band (holes) without changing the band gap within the one quantum well is possible. The built-in potential changing within the one quantum well is 43meV in the actual built-in electric field if the built-in voltage is assumed to be 0.65V, the thickness of the i-layer inclusive of a MQW absorption layer to be 0.18μm and the width of the well layer to be 12nm and, therefore, the negation of the built-in electric field is made possible by this structure.
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