Research on THz laser utilizing deep impurities in semiconductors

我们证实了Si: P中的太赫兹激光振荡，并通过红外光电性研究了Ge: As、Ge: Zn和Ge: Te中的杂质能级，讨论了太赫兹激光振荡的可能性。德国DLR研究所提供了一个5×7×7mm^3矩形的Si: P样品，六个平行表面精确抛光。将其置于He液体中，用1MW TEA CO_2激光激发。用Ge: As探测器探测太赫兹辐射。由于发射强度对激发光的入射角敏感，并且发射强度依赖于激发光的阈值，因此我们确定了激光。在TEA CO_2激光激发下，测量了Ge: As和Ge: Zn的红外光导率。Ge: As和Ge: Zn分别呈超线性和亚线性关系。我们测量了红外光导率，详细研究了锗中的杂质水平。除了声子吸收外，Ge: As和Ge: Zn分别在120 meV和115 meV左右出现了光导率的下降。两个m都对应于自由电子通过发射LO声子跃迁到杂质激发态。在Ge: Te中，观察到类似范诺共振的结构，估计ls（T2）激发态的电离能为10.5meV。Ge中深层杂质所利用的太赫兹激光振荡在5meV左右，远低于Si: P激光，因为尽管有深层杂质，但ls（T2）态相当浅。

We have confirmed THz laser oscillation in Si : P and discussed possibility of THz laser oscillation by investigating impurity level by infrared photoconductivity in Ge : As, Ge : Zn and Ge : Te. DLR Institute in Germany supplied a Si : P sample of 5×7×7mm^3 rectangular shape with six parallel surfaces polished exactly. It was placed in liquid He and excited by 1MW TEA CO_2 laser. THz emission was detected a Ge : As detector. We confirmed lasing because emission intensity is sensitive to the incident angle of excitation light and the emission has a threshold in excitation intensity dependence. In order to characteristic of the detector infrared photoconductivity was measured in Ge : As and Ge : Zn eicited by TEA CO_2 laser. Super and sub linear dependences were observed fofr Ge : As and Ge : Zn, respectivevly. We measured infared photoconductivity to study impuritylevel in Ge in detail. In addition to phonon absorption, decrease of phohtoconductivity was observed around 120 and 115 meV in Ge : As and Ge : Zn, respectively. Both of the m correspond to transition of a free electron to the excited state of impurity by emitting LO phonon. In Ge : Te, structures like Fano resonances were observed and the ionization energy of ls(T2) excited state was estimated to be 10.5meV. The THz laser utilized by deep impurities in Ge may oscillate around 5meV much lower than Si : P laser because the ls(T2) state is considerably shallow in spite of a deep impurity.