| 摘要 |
PROBLEM TO BE SOLVED: To satisfy both high speed operation and high optical output operation by forming a modulator part on a semiconductor layer having carrier concentration of a specified level or below and forming a laser part on a semiconductor layer having carrier concentration of a specified level or above. SOLUTION: A modulator integrated DFB laser comprises an n-type InP substrate 101, a laser part 104 provided with a diffraction grating 105 formed on the substrate 101, and a modulator part 102 disposed contiguously to the laser part 104. The modulator part 102 is provided on a 0.3μm thick lightly doped layer having carrier concentration of 1×1017 cm-3, i.e., an n- layer 103. The DFB laser part 104 is formed on the heavily doped InP substrate 101 having carrier concentration of 1×1018 cm-3. Consequently, pin junction capacity formed by a buried layer and the substrate can be reduced in a reverse operation modulator. In the DFB laser, leakage current of the buried layer is prevented from increasing without lowering the built-in voltage of pn junction formed in the buried layer.
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