| 摘要 |
PURPOSE:To provide a direct-transition semiconductor, in which the probability of transition by light between the conduction band and valence band is increased, by a zone-folding of energy band. CONSTITUTION:A cubic crystal structure is provided in which its unit cell includes atomic silicon layers and atomic germanium layers stacked in the (111)-plane, and the silicon and germanium layers totals to an even number; a zone-folding of energy band is shown in the figure. In the figure are shown the gamma point in a wave-vector space 11, the L point 12, a conduction band 14, a valence band 15, and a conduction band 16 that contains silicon atoms only. In such a semiconductor, the L point is folded onto the gamma point, so it becomes a direct-transition semiconductor having the gamma point on the bottom of the conduction band. The L point in the wave-vector space, whose symmetry is owing more than 50% to the s-orbit, is folded onto the gamma point. Therefore, it is possible to increase the probability of transition by light between the conduction band and valence band. |
