| 摘要 |
PURPOSE:To realize a high speed modulation by a method wherein a semiconductor layer is provided to the inside of a clad layer so as to make its side face brought into contact with a buried layer, and a built-in voltage at the contact face is made lower than one between the above clad layer and the buried layer. CONSTITUTION:An n-type InGaAsP layer 8 and an n-type InP clad layer 9 are inserted in between an n-type InP substrate 1 and an InGaAsP active layer 2. And, a built-in voltage of an interface, where the n-type InGaAsP layer 8 and a P-type InP buried layer 4 are brought into contact with each other, is made smaller than that of an interface where the buried layer 4 and the substrate 1 which serves also as a clad layer are brought into contact with each other. By these processes, the rise of a current of a pn junction composed of the buried layer 4 and the layer 8 is made faster than that of a pn junction composed of the buried layer 4 and the substrate 1, so that a parasitic capacitance between electrodes 6 and 7 is made to decrease and a high speed modulation can be realized. |
