具有矽鍺P型高摻雜區的矽/矽鍺超晶格發光二極體特性研究

Abstract

矽鍺光電元件具有與矽積體化電路整合的優點，加上量子異質接面結構的長晶技術進步，因此近年來矽鍺異質接面的光電元件被廣為研究。而本論文中提出室溫操作且發光波段在1.3-1.4微米之多週期矽/矽鍺超晶格發光二極體。 在本篇論文中我們利用超高真空化學氣相沈積成長十週期的矽/矽鍺超晶格結構，並在P型高掺雜區域分別成長了矽塊材以及矽鍺塊材兩種不同的材料，分別稱作樣品A及樣品B，以探討P型高掺雜區，除了作為歐姆接點外，對於矽/矽鍺超晶格電激發光特性之影響，特別是在發光頻譜的變化。根據實驗結果，我們發現矽鍺於導帶會比矽高出△Ec，故擴散至矽鍺P側的電子會被其擋住而累積在矽與超晶格部分，而造成電子的濃度上升。另外，矽鍺於價帶亦比矽高出△Ev，因而會阻擋部份由P側注入的電洞，造成低溫下電洞主要累積在矽鍺高掺雜區及超晶格區，而只能觀察到矽鍺塊材與超晶格的光。常溫下電洞不容易被量子井及矽鍺的價帶侷限，因此受矽鍺高掺雜區影響，樣品B可以觀察到相對於樣品A強的矽發光。總和來說，矽鍺高掺雜層在低溫下可抑制矽發光而得到矽鍺塊材及超晶格的光，而在常溫下則可稍微增幅矽發光。

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.