Terahertz radiation by spontaneous polarization fields in InN |
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| Affiliation: | 1. Institute of Microelectronics Technology and High-purity Materials, Russian Academy of Science (IMT RAS), 6 Academician Ossipyan str., Chernogolovka, Moscow 142432 Russian Federation;2. Institute of Problems of Chemical Physics of Russian Academy of Sciences (IPCP RAS), 1 Academician Semenov av., Chernogolovka, Moscow 142432 Russian Federation;3. Chernogolovka Scientific Center, Russian Academy of Sciences, Chernogolovka, Moscow 142432, Russian Federation;4. Laboratory of Electron Microscopy, Faculty of Biology, Lomonosov Moscow State University, Moscow 119991, Russian Federation;1. School of Materials Science and Engineering, Kyungpook National University (KNU), Daegu 41566, South Korea;2. Department of Physics, Le Quy Don Technical University, No. 236 Hoang Quoc Viet Street, Hanoi, Viet Nam;3. School of Engineering Physics, Hanoi University of Science and Technology (HUST), No. 01 Dai Co Viet Street, Hanoi, Viet Nam;4. KNU Advanced Material Research Institute, Kyungpook National University, Daegu 41566, South Korea |
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| Abstract: | Terahertz (THz) radiation is measured from InN excited by femtosecond optical pulses at 790 nm. The InN sample is grown by metalorganic chemical vapor deposition. The InN surface shows typical grain like morphology often observed in N-polar InN. The polarity of the THz radiation field from InN is opposite to that from p-InAs, whose radiation mechanism is dominated by the photo-Dember effect, and is same as that from p-GaAs indicating that the dominant radiation mechanism in InN is the drift current induced by the internal electric field at low-density excitation. In addition, since no azimuthal angle dependence of the THz radiation is observed, the optical rectification effect is ruled out. The lattice constant c=5.7091 Å for the InN epilayer is determined by θ–2θ scan of X-ray diffraction. This implies that the InN epilayer is fully relaxed. Therefore, there is no piezoelectric polarization, and the internal electric field in the InN epilayer results from spontaneous polarization. According to the direction of the spontaneous polarization, the N polarity of the InN sample is confirmed. |
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