ELECTRON-HOLE CONDENSATION IN SEMICONDUCTORS
ELECTRON-HOLE CONDENSATION IN SEMICONDUCTORS
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DOI：
10.1126/science.189.4207.955
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发表时间：
1975-01-01
期刊：
影响因子：
56.9
通讯作者：
JEFFRIES, CD
中科院分区：
文献类型：
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作者：
JEFFRIES, CD
在Ge和Si以及Ge-Si合金中，有大量证据表明电子和空穴在恒定密度的冷等离子体中稳定结合，并经历相分离。形成尺寸为1 ~ 300 μm的液态金属液滴，寿命为0.1 ~ 600 μsec。对于锗，已知的数量惊人：相图、表面能、功函数、衰变动力学。Si的知名度要低得多。液体密度、临界密度、临界温度和结合能的理论值与实验值吻合较好。液相的稳定性明显地依赖于能带结构。Si、Ge和Ge-Si的多谷结构和质量各向异性，以及它们的间接带隙，无疑是这些晶体中观察到的稳定性的原因。在类似的半导体磷化镓中，尚未观察到液滴，很可能是因为高杂质含量捕获了激子。在砷化镓中液滴的存在是有争议的。毫无疑问，在其他半导体中也会发现液滴，也许温度更高。对实验学家来说，这是一个令人兴奋的领域；新现象被迅速发现，通常在它们被预测之前。对于理论物理学家来说，电子空穴下降具有很高的内在意义。它是周期性晶格中密度恒定的量子液体的第一个例子。许多具有挑战性的实验和理论问题仍然存在。
In Ge and Si, and also in Ge-Si alloys, there is extensive evidence for the stable binding of electrons and holes into a cold plasma of constant density, which undergoes a phase separation. Liquid metallic drops 1 to 300 μm in size are formed, with lifetimes ranging from 0.1 to 600 μsec. For Ge a surprising amount is known: the phase diagram, the surface energy, the work function, the decay kinetics. Much less is known for Si. There is good agreement between theoretical and experimental values of the liquid density, the critical density, the critical temperature, and the binding energy. The stability of the liquid phase is strikingly dependent on band structure. The multivalley structure and mass anisotropy of Si, Ge, and Ge-Si, together with their indirect band gap, are no doubt responsible for the observed stability in these crystals. In the similar semiconductor gallium phosphide, drops have not yet been observed, most likely because the high impurity content traps the excitons. In gallium arsenide the existence of drops is controversial. Undoubtedly drops will be found to exist in other semiconductors, perhaps at even higher temperatures. This is an exciting field for the experimentalist; new phenomena are being rapidly discovered, usually before they are predicted. For the theorist, the electron-hole drop is of high intrinsic interest. It represents the first example of a quantum liquid of constant density in a periodic crystal lattice. A number of challenging experimental and theoretical problems remain.