MIOMD-XI Speakers    
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1.  Dr. Manabu Mitsuhara, NTT Corporation, JAPAN
Late-Breaking Results: High responsivity InGaAsSb/InP p-i-n photodetectors operating at wavelengths exceeding 1.8 μm
Speaker Biography: Manabu Mitsuhara: He received the B.E. and M.E. in applied physics and the Ph.D. degree in engineering from Osaka University in 1989, 1991, and 2000, respectively. In 1991, he joined NTT Optoelectronics Laboratories. From 2000 to 2003, he worked for new business development in the area of e-Learning at NTT Communications Corporation. He is currently engaged in research and development of semiconductor photonic devices. His research interests include development of midinfrared lasers using strained InGaAs quantum wells and InGaAsSb, InGaAsN infrared photodetectors.

Summary: Photodetectors (PDs) operating at a wavelength around 2 um is useful for industrial and environmental applications in spectroscopy. Here we describe the growth of InGaAsSb by MOMBE and its application to a PD absorption layer, since a bandgap of InGaAsSb is smaller than that of InGaAs under nearly lattice-matched conditions with InP. The samples were grown on InP substrates at 500-510 °C. For the application of InGaAsSb as a PD absorption layer, both a bandgap reduction and a low background carrier concentration are crucial. The use of TDMASb as an Sb source was effective in decreasing the bandgap and the carrier concentration of InGaAsSb. The TDMASb supply greatly reduced the C incorporation into the film to the detection limit, corresponding to a C concentration of 5×1016 cm-3. The background carrier concentration of the InGaAsSb layer was 2×1015 cm-3, which was about one twentieth that of the InGaAs layer. This is due to the low C impurity incorporation. In contrast, the Sb incorporation into the film increased with the TDMASb supply, and the incorporated Sb resulted in an increase in the photoluminescence peak wavelength. By introducing a small strain (+0.1%) into the InGaAsSb, the photoluminescence peak wavelength reached 1.8 um, and then we used it as the absorption layer of a p-i-n PD. The fabricated PD had a cutoff wavelength longer than 1.8 um, and the responsivity was constant at 1A/W over a wide wavelength range of 1.4 to 1.7 um. The responsivity of about 1 A/W remained unchanged even when the reverse bias voltage was reduced from 3 to 0.1 V, with an incident wavelength of 1.65 um.
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