| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 93 === The advantage of the optoelectronic component of silicon germanium is fully compatible with the Si-based microelectronic chips. In addition, the progress of the growth techniques for quantum heterojunction structure is in advanced. So the heterojunction structure of silicon germanium is studied far and wide in recent years. In this thesis, the light-emitting diodes (LEDs) with multi-periods of Si/SiGe superlattice operating at room temperature for 1.3-1.4μm emission wavelength are reported.
We design a ten periods Si/SiGe superlattice structure that is grown by UHV/CVD system in this thesis, and two materials of Si and SiGe bulk are grown in P+ doped region, called sample-A and sample-B separately. Then we analyze the influences of the P+ doped region on electroluminescence characteristics, especially the electroluminescence (EL) spectra. According to experimental results, we find that because conduction band of SiGe is higher than that of Si, the electrons that diffuse to P side will be blocked and accumulate in the region of Si buffer and superlattice, and causes the electrons density grow up. Besides, the valence band of SiGe is also higher than Si, so that will block a part of injection holes, causes holes accumulate in the regions of P+ doped SiGe and superlattice at low temperature, and the light emitting from SiGe bulk and superlattice only can be observed. Holes aren’t easily confined in superlattice and the valence band of the SiGe bulk at room temperature, so we can observe stronger Si light emitting in sample-B than sample-A by the effect of the P+ doped SiGe region. Conclusively, the P+ doped SiGe layer can suppress the Si light emitting so we can observe the light emitting from SiGe bulk and superlattice at low temperature, and it can enhance the Si light emitting at room temperature.
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