Carrier dynamics of Mg-doped indium nitride
Carrier dynamics of Mg-doped indium nitride
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掺镁氮化铟的载流子动力学
DOI：
10.1117/12.874133
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
S. Gwo
中科院分区：
文献类型：
--
作者：
H. Ahn;Chao;Y. Hong;S. Gwo
本文研究了Mg掺杂InN（InN：Mg）薄膜的载流子动力学随载流子密度的变化规律。最近，我们已经证明了一个显着的增强太赫兹发射InN：Mg，这是由于漂移和扩散电流的时间演变取决于背景载流子密度。我们研究了InN：Mg的载流子动力学的细节，这是至关重要的澄清太赫兹发射机制进行时间分辨的光学反射率测量上生长的InN：Mg薄膜与不同的Mg掺杂水平。实验分析表明，InN：Mg薄膜反射率响应的初始急剧下降和恢复主要是由光生载流子相关的带隙重整化和带填充过程控制的，而InN：Mg薄膜反射率的慢衰减时间常数（τ2）与背景载流子浓度有很强的依赖性。随着载流子密度从未掺杂的InN的载流子密度降低，InN：Mg的τ2持续增加，并且在约1 × 1018 cm-3的临界值处达到最大值。有趣的是，在此载流子密度下观察到最强的太赫兹辐射，并且随着载流子密度的增加而减小。强太赫兹辐射对应于通过扩散和漂移的带电载流子密度的快速和大的空间分离。大的空间间距导致了太赫兹波强发射后带电载流子达到平衡的衰减时间较长，解释了太赫兹辐射与τ2具有相似的载流子密度依赖性。
We report the carrier density dependence of carrier dynamics of Mg-doped InN (InN:Mg) films. Recently, we have demonstrated a significant enhancement of terahertz emission from InN:Mg, which is due to the temporal evolution of drift and diffusion currents depending on the background carrier density. We studied the details of carrier dynamics of InN:Mg which is crucial for the clarification of the terahertz emission mechanism by performing the time-resolved optical reflectivity measurement on InN:Mg films grown with different Mg-doping levels. Experimental analysis demonstrates that the initial sharp drop and recovery of reflectivity response of InN:Mg films are dominated by photocarrier-dependent bandgap renormalization and band filling processes, whereas the slow decay time constant (τ2) of reflectivity of InN:Mg has the strong dependence on the background carrier density. As the carrier density decreases from that of undoped InN, τ2 of InN:Mg continuously increases and reaches the maximum value at a critical value of ~1x1018 cm-3. Interestingly, the strongest terahertz radiation was observed at this carrier density and it keeps decreasing with the increase of carrier density. Intense terahertz radiation corresponds to the fast and large spatial separation of charged carrier density through diffusion and drift. Large spatial separation results in the longer decay time for charged carriers to reach equilibrium after strong emission of terahertz waves, and it explains the similar carrier density dependence of terahertz emission and τ2.