Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2012 Jan 13;108(2):026401. doi: 10.1103/PhysRevLett.108.026401. Epub 2012 Jan 11.
Hyperdoping has emerged as a promising method for designing semiconductors with unique optical and electronic properties, although such properties currently lack a clear microscopic explanation. Combining computational and experimental evidence, we probe the origin of sub-band-gap optical absorption and metallicity in Se-hyperdoped Si. We show that sub-band-gap absorption arises from direct defect-to-conduction-band transitions rather than free carrier absorption. Density functional theory predicts the Se-induced insulator-to-metal transition arises from merging of defect and conduction bands, at a concentration in excellent agreement with experiment. Quantum Monte Carlo calculations confirm the critical concentration, demonstrate that correlation is important to describing the transition accurately, and suggest that it is a classic impurity-driven Mott transition.
超掺杂已经成为设计具有独特光学和电子特性半导体的一种很有前途的方法，尽管这种特性目前缺乏明确的微观解释。我们结合计算和实验证据，探究了 Se 超掺杂 Si 中亚带隙光学吸收和金属性的起源。我们表明，亚带隙吸收来自于直接缺陷到导带的跃迁，而不是自由载流子吸收。密度泛函理论预测，Se 诱导的绝缘到金属转变是由缺陷带和导带的合并引起的，其浓度与实验非常吻合。量子蒙特卡罗计算证实了临界浓度，表明相关性对于准确描述跃迁很重要，并表明这是一个典型的杂质驱动的莫特转变。
