Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 87: Goup IV elements and their compounds II

HL 87.1: Talk

Thursday, March 14, 2013, 15:45–16:00, H15

Indirect to direct gap transition in strained and unstrained group-IV semiconductor alloys — Christian Eckhardt, •Kerstin Hummer, and Georg Kresse — University of Vienna, Computational Materials Physics, Sensengasse 8/12, 1090 Vienna, Austria

The basic problem of the well established Si technology is the indirect nature of the fundamental band gap of the elemental group-IV semiconductors resulting in inefficient light absorption and emission. To overcome these limitations, advanced (opto)electronic device design concentrates on strategies to transform materials consisting of group-IV elements from indirect into direct gap semiconductors. One promising route established is the introduction of strain either by alloying or by growing heterostructures/superlattices. Besides the extensively investigated Si/Ge system, the Sn_xGe_1−x alloy turned out to be very promising [1].

In this work, we focus on Sn_xGe_1−x and C_xGe_1−x random substitutional alloys. The transition from an indirect to a direct gap semiconductor in strained and unstrained alloys as a function of the Sn/C content between 0 ≤ x ≤ 0.5 is investigated within density functional theory by means of both, a supercell approach and the Virtual Crystal Approximation. Accurate band structures are obtained with the modified Becke-Johnson exchange potential in combination with LDA correlation [2].
[1] H. Lin et al., Appl. Phys. Lett. 100, 102109 (2012)
[2] F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401 (2009)