Research of High-Efficiency Silicon-Based Light-Emitting Devices

点击翻译按钮获取中文摘要

Electronic structures are investigated for Si/Ge manmade crystals using an sps^* tight binding model. For the crystal stacked with two monolayrs of Si and Ge, wavefunction of electrons at the GAMMA point is very similar to that at the L point in bulk Ge, and thus the energy takes the local minimum in the conduction band at the GAMMA point. By elongating the bond length, the crystal takes the direct-transition type structure.This crystal, having potentially visible light emission characteristics, is difficult to be formed by conventional epitaxial methods based on random chemisorption of atoms. Thus an atomic layr epitaxy (ALE) method has been investigated where the crystal is grown with a layr-by-layr manner. The Si-ALE method has been achieved using newly introduced atomic hydrogen and SiH_2Cl_2, for the first time, with an ideal (one monolayr per cycle) growth rate. And the Ge-ALE with the ideal growth rate has been also demonstrated by alternative exposure to atomic hydrogen and GeH_2 (CH_3) _2 for a wide temperature range from 400ﾟC to 518ﾟC.Ge- and Si- hetero ALEs, i.e., growth of Ge on Si and that of Si on Ge, has been investigated for making the manmade crystals. As for the former, there was a problem that the surface is covered by Ge of one monolayr. As for the latter, there was a problem that a lot of carbon atoms are adsorbed on the surface.