| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical semiconductor device which is excellent in element isolation characteristic and wide in modulation bandwidth by a method wherein an optical modulator equipped with a current blocking structure where an N-type InP hole blocking layer specified in carrier concentration is inserted into a semi-insulating Fe-doped InP layer and a DFB laser are integrated. SOLUTION: Semi-insulating Fe-doped InP layers 8 and 10 are buried in both sides of a mesa structure composed of multi-quantum well layers 4 and 11 and clad layers 26 and 27, and an N-type InP hole blocking layer 9 is inserted into the Fe-doped InP layers 8 and 10 for the formation of a current blocking layer, wherein the N-type InP hole blocking layer 9 is set ranging from 1×10<18> cm<-3> to 4×10<18> cm<-3> in carrier concentration. By this setup, an RF signal leakage from a modulator 102 to a laser 101 is limited to -30dB or less, and the laser 101 can be kept free from kinks. Therefor, an optical semiconductor device which is excellent in element isolation characteristics and wide in modulation bandwidth can be obtained, where elements are capable of displaying their performances enough.
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