| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2003: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2002: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
The followings are the summary of research conducted based on the proposal submitted on September 2002.
[1]Observation of Shubnlkov-da Haas measurements of Si-doped InN
With the collaboration with Dr.Higashiwaki of Communications Research Laboratory of Independent Administrative Institution, we succeeded to grow Si-doped InN with the carrier concentration from 2×10^<18>cm^<-3> to 1.5×10^<19>cm^<-3> and the mobility of 1600 cm^2V^<-1>s^<-1>. These samples did not show any resistivity anomaly down to 0.5 K. The samples, however show clear Shubnikov-de Haas oscillations when the carrier concentration is less than 5×10^<18>cm^<-3>. From the analysis of the Shubnikov-de Haas oscillation of angle dependence between the applied magnetic field and crystal c axis, we concluded that the electronic structure of InN consists of two components ; one is the Fermi surface with spherical 3-dimensional distribution. The other is the one spread one dimensionally on a-b plane. The electronic structure of I
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nN was reported 5^<th> International Conference of Nitride Semiconductors held at Nara 2003.
[2]Optical properties of Si-doped InN
Carrier concentration dependence of the interaction between free carriers and LO phonons of InN is studied by Raman scattering and FfIR measurements The carrier concentration is varied from 1.8×10^<18> to 1.5×10^<19>cm^<-3> by Si-doping. The infrared reflection spectra, to which the vibration in the a-b plane contributes, reveal linear-coupling between the E_1(LO) phonon and the plasma oscillation of the free carriers. From the plasma frequency the electron effective mass is estimated to be m^*_e=0.085 m_o for the intrinsic InN. The Raman spectra, to which the vibration along the c-axis contributes, reveal that the A_1(LO) phonon and free carriers couple non-linearly, where Fano interference between the zone-center LO phonon and the quasicontinuum electronic state along the c-axis is prominent. With these results, the anisotropic electronic structure of InN was discussed
[3]The relationship between the superconductivity and impurities of InN
We present the carrier concentration dependence of the absorption, luminescence and Raman spectra of InN grown by MBE on sapphire (0001) surface in the carrier concentration region where superconductivity was observed The carrier concentration was changed from 2×l0^<19>cm^<-3> to 7×10^<20>cm^<-3> by Mg and Dy impurities. The band gap energy increased as the concentration increased, but the luminescence peak remained at around 0.8 eM The Fano resonance observed at the A_1(LO) phonon became stronger when the carrier concentration increased. There was an optimum carrier concentration region for the superconductivity of InN to occur.. Less
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