Crystal Growth of Thallium Containing III-V Semimetal-Semiconductor Alloys and Search of New Physical Properties

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Quaternary semiconductors TlInGaAs, TlInGaP were grown on InP substrates by gas source MBE using elemental Tl, In and Ga, and thermally cracked arsine and phosphine.Substrate temperature during growth was 450ﾟC.X-ray diffraction and EPMA measurements confirmed the successful growth of TlInGaAs and TlInGaP.It was found that Tl composition of TlInGaAs increases with Tl flux during growth.Photoluminescence (PL) emission was observed from the grown TlInGaAs.PL peak wavelength was observed to increase with Tl composition and it was found that the bandgap is decreased by incorporation of Tl.Temperature dependence of PL spectra showed that the temperature variation of bandgap energy is slower than those of GaAs, InP and InAs.For the TlInGaAs with Tl composition of 6%, nearly temperature-independent bandgap energy was observed.This result agrees well with our expected properties.We also have grown the double-hetero (DH) structure of InP/TlInGaAs/InP.From the X-ray diffraction and EPMA measurements on this DH structure showed that the interdiffusion of group III atoms at the interfaces was not occurred.Furthermore, we have observed the enhancement of PL intensities from TlInGaAs layer by the formation of DH structures.Slower temperature variation of bandgap energy was also observed for TlInGaP by the measurement of temperature dependence of photoconductance spectra.We have observed the TIP Raman signals for the first time.The Raman peaks were located at lower wavenumbers of those of InP.It was suggested that TlInGaAs is promising for the application to the temperature-independent wavelength laser diodes.