Electronic structure and carrier dynamics of the ferromagnetic semiconductor Ga 1¿x Mn x As
Electronic structure and carrier dynamics of the ferromagnetic semiconductor Ga 1¿x Mn x As
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DOI：
10.1103/physrevb.68.165204
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发表时间：
2003-10
影响因子：
3.7
通讯作者：
E. J. Singley;K. Burch;R. Kawakami;J. Stephens;D. Awschalom;D. Basov
中科院分区：
文献类型：
--
作者：
E. J. Singley;K. Burch;R. Kawakami;J. Stephens;D. Awschalom;D. Basov
红外光谱用于研究铁磁半导体 Ga1-xMnxAs 中能隙内吸收的掺杂和温度依赖性，从顺磁 x=0.017 样品到重掺杂 x=0.079 样品。透射率和反射率测量与 Kramers-Kronig 分析相结合，使我们能够确定薄膜的光学常数。所有铁磁样品在 GaAs 带隙内都显示出 200 meV 附近的广泛吸收共振。我们对该特征的可能起源进行了批判性分析，包括锰引起的杂质带和间隔带跃迁。频率相关电导率实部的总体幅度随着 Mn 掺杂的增加而增长，并在 x=0.052 样本中达到最大值，其中 T-C 在该系列的最高值（类似于 70 K）处饱和。我们观察补偿的光谱特征，并跟踪其对 Mn 相图电子和磁态的影响。远红外光谱的温度依赖性揭示了铁磁态下流动载流子的有效质量显着降低。质量变化和样品磁化强度之间的简单比例关系表明，巡回载流子在该系统中产生铁磁性方面发挥着关键作用。
Infrared spectroscopy is used to study the doping and temperature dependence of the intragap absorption in the ferromagnetic semiconductor Ga1-xMnxAs, from a paramagnetic, x=0.017 sample to a heavily doped, x=0.079 sample. Transmission and reflectance measurements coupled with a Kramers-Kronig analysis allow us to determine the optical constants of the thin films. All ferromagnetic samples show a broad absorption resonance near 200 meV, within the GaAs band gap. We present a critical analysis of possible origins of this feature, including a Mn-induced impurity band and intervalence band transitions. The overall magnitude of the real part of the frequency dependent conductivity grows with increasing Mn doping, and reaches a maximum in the x=0.052 sample where T-C saturates at the highest value (similar to70 K) for the series. We observe spectroscopic signatures of compensation and track its impact on the electronic and magnetic state across the Mn phase diagram. The temperature dependence of the far infrared spectrum reveals a significant decrease in the effective mass of itinerant carriers in the ferromagnetic state. A simple scaling relation between changes in the mass and the sample magnetization suggest that the itinerant carriers play a key role in producing the ferromagnetism in this system.