Size effect on high temperature variable range hopping in Al+ implanted 4H-SiC
Size effect on high temperature variable range hopping in Al+ implanted 4H-SiC
复制标题
Al 注入 4H-SiC 中高温可变范围跳跃的尺寸效应
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
R. Nipoti
中科院分区：
文献类型：
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作者：
A. Parisini;A. Parisini;R. Nipoti
分析了Al注入浓度为3 × 1020 cm-3和5 × 1020 cm-3的重掺杂4 H-SiC（Al）层在1950-2100 °C退火后的空穴输运特性，确定了主要的输运机制。这项研究表明，电阻率（电导率）的温度依赖性可能是由一个可变范围跳跃（弗赫）运输到杂质带。取决于注入杂质的浓度和注入后退火处理，这种弗赫机制在可以延伸到室温的不同温度范围内持续存在。在这个框架中，两个不同的传输机制被确定，具有各向同性的三维弗赫和各向异性的近二维弗赫的特性。后一种传导机制似乎发生在一个相当厚的层（约400 nm），这是太大，以引起限制效应的载流子跳跃。被认为是一个各向异性运输的可能性，由于在注入层中的高密度的基面堆垛层错（SF）的注入层的结构修改可能引起的。对本研究中一个5 × 1020 cm−3 Al注入样品的透射电子显微镜（TEM）研究结果支持了根据近2D弗赫对最重掺杂样品中导电性的解释。在这种情况下，沿沿着c轴测量的基面SF之间的平均间隔（其与电表征期间的载流子输运正交）似乎与弗赫理论的最佳跳跃长度的估计值一致。相反，在Al浓度为1 × 1019 cm−3的样品中，通过TEM没有检测到SF，其中观察到3D最近邻跳跃（NNH）输运。
The hole transport properties of heavily doped 4H-SiC (Al) layers with Al implanted concentrations of 3 × 1020 and 5 × 1020 cm−3 and annealed in the temperature range 1950–2100 °C, have been analyzed to determine the main transport mechanisms. This study shows that the temperature dependence of the resistivity (conductivity) may be accounted for by a variable range hopping (VRH) transport into an impurity band. Depending on the concentration of the implanted impurities and the post-implantation annealing treatment, this VRH mechanism persists over different temperature ranges that may extend up to room temperature. In this framework, two different transport regimes are identified, having the characteristic of an isotropic 3D VRH and an anisotropic nearly 2D VRH. The latter conduction mechanism appears to take place in a rather thick layer (about 400 nm) that is too large to induce a confinement effect of the carrier hops. The possibility that an anisotropic transport may be induced by a structural modification of the implanted layer because of a high density of basal plane stacking faults (SF) in the implanted layers is considered. The interpretation of the conduction in the heaviest doped samples in terms of nearly 2D VRH is supported by the results of the transmission electron microscopy (TEM) investigation on one of the 5 × 1020 cm−3 Al implanted samples of this study. In this context, the average separation between basal plane SFs, measured along the c-axis, which is orthogonal to the carrier transport during electrical characterization, appears to be in keeping with the estimated value of the optimal hopping length of the VRH theory. Conversely, no SFs are detected by TEM in a sample with an Al concentration of 1 × 1019 cm−3 where a 3D nearest neighbor hopping (NNH) transport is observed.