Study on New Semiconductors for Temperature-insensitive Wavelength Semiconductor Lasers

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A new semiconductor material consisting of semiconductor and semimetal which has a temperature-insensitive band gap has been studied to develop a semiconductor laser whose wavelength does not change when the ambient temperature Changes. The detailed growth conditions and the characteristics of GaAs_<1-x>Bi_x semiconductor alloy layers have been studied. The lattice constants of the alloy were found to increase with the addition of Bi. The uniformity and the reproducibility of the solid composition of the GaAs_<1-x>Bi_x epilayers are good in spite of the difficulty of epitaxial growth. Although layer growth was performed at a low temperature, the stability of GaAs_<1-x>Bi_x alloy was sufficient for device processing. The photoluminescence (PL) spectra show that the PL peak energy of the GaAs_<1-x>Bi_x alloy shifts to a longer wavelength with increasing Bi content. The temperature dependence of the PL peak energy is much weaker than the temperature variation of the band gap of GaAs. The results obtained in this research support the hypothesis that III-V alloy semiconductors consisting of semiconductor and semimetal components have a temperature-insensitive band gap.To create a semiconductor material of optical fiber communication wavelength, GaInAsBi alloy has been targetted. The epitaxial growth of GaInAs, the host crystal of the alloy, was examined at low temperatures. Using new method, GaInAs layers of good optical quality were grown even at 420 C. However the growth temperature could not be lowered any further even using a new Ga precursor, TiPGa. New precursors of Ga and In which enable the growth of GaInAs at 365 C are expected, which will allow the growth of the new GaInAsBi alloy.