Investigation of electronic structure and electron conduction mechanism of InN

InN的电阻率的温度依赖性作为载流子密度的函数进行了研究。通过Si掺杂，载流子密度从n_e= 1.8 × 10 ~（-3）cm ~（-3）<18><-3>变为1.5 × 10 <19><-3>~（-3）cm ~（-3）。研究的InN在20 K以上表现出金属导电性。在较低的温度下，有一个电阻率异常起源于载流子局域化的a-b平面，这是证实了在0.5 K的磁阻。Shubnikov de-Haas振荡表明InN具有球形费米面，当n_e&lt;5 × 10 ~（10）cm ~ 2时，其半径随ne的增大而增大<18><-3>。此外，在垂直于a-b平面施加的电场中观察到对应于恒定载流子密度4.5 × 10 ~（-4）<12>cm ~<-2>（-1）的振荡。这种振荡表现出对磁场的异常角度依赖性。考虑到这个密度，我们确定莫特跃迁的临界载流子密度为2x 10 ^<17>cm^2<-3>。在a-b平面内观察到各向异性的局域化，这表明电子在a-b平面内的分布是不均匀的。根据这些结果，给出了生长在蓝宝石（0001）上的InN的基本吸收边的电子结构，而载流子密度n_e低至4 × 10 ~（-3）cm ~（-1）的样品<17><-3>显示出超导性，其T_c= 0.47 K（中点）。在层状铜氧化物高温超导体中，InN的涡旋固体被热涨落和外磁场熔化。临界电流J_c随磁场的变化在很宽的磁场范围内呈指数衰减，这是由于电流在微约瑟夫森结中的隧穿作用。我们提出了一种机制，其中J_c的各向异性与ab平面上有限长In-In链的存在有关。

Temperature dependence of the resistivity of InN was investigated as a function of carrier density. The carrier density was changed from n_e=1.8x10^<18>cm^<-3> to 1.5x10^<19>cm^<-3> by Si doping. The InN investigated showed metallic conduction above 20 K. At lower temperatures there was a resistivity anomaly originating from carrier localization in the a-b plane, which was confirmed by the magnetoresistance at 0.5 K. The Shubnikov de-Haas oscillation showed that InN had a spherical Fermi surface and its radius increased according to the increase of ne when n_e<5x10^<18>cm^<-3>. In addition an oscillation corresponding to the constant carrier density of 4.5x10^<12>cm^<-2> was observed in the field applied perpendicular to the a-b plane. This oscillation showed an anomalous angle dependence on the magnetic field. Taking into account this density, we determined the critical carrier density of the Mott transition to be 2x10^<17>cm^<-3>. Anisotropy of localization was observed within the a-b plane, which indicates that the distribution of the electrons was not uniform in the a-b plane. From these results, an electronic structure at the fundamental absorption edge of InN grown on sapphire (0001) was presented.On the other hand, samples with carrier densities n_e as low as 4x10^<17>cm^<-3> show superconductivity with T_c= 0.47 K (midpoint). As in the layered cuprate high Tc superconductors, the vortex solid of InN is melted by thermal fluctuation and by the external magnetic field. The field dependence of the critical current J_c exhibits an exponential decay over a wide range of magnetic field, which is ascribed to the current tunneling through micro Josephson-junctions. We propose a mechanism where the anisotropy of J_c is related to the presence of In-In chains of finite length in the ab plane.