Abstract
摘要:電子工業已於1998 年超越汽車工業,達一兆美元之市場,是目前臺灣及世界之重
要工業。另一方面,光電工業也正在蓬勃發展當中,而將成為另一主流之一,這兩
類工業都相當倚重半導體材料。然而電子工業所用的材料是矽,屬於間接能隙材料,
而光電工業所用的發光材料是直接能隙材料。材料的不同,使得電子產品與光電產
品的整合非常不容易,假如兩者的材料相同,那麼電子工業和光電工業的匯流將對
二十一世紀產生更大的影響。由於矽半導體的製造技術相當成熟,所以電子工業將
仍以矽半導體材料為主,若是可以使間接能隙的矽材料也能電激發光,將使光電工
業很快地與電子工業結合,使兩者獲有相得益彰的發展。此外,電子晶片的速度不
斷提高,但晶片間訊號的導線傳輸速度,不易相對提升,因此改用光波傳輸以取代
導線傳輸,長久以來就被認為是突破的解決方式。但電子晶片所用的矽材料是間接
能隙,過去的技術難以讓它發光,使得光波傳輸的方式難以實現,若是矽晶片也能
電激發光,晶片間訊號傳輸速度就能繼續提高。然而間接能隙的矽材料可能電激發
光嗎? 過去的半導體技術持否定的答案,但是在不斷進步的半導體技術下,此障礙
可以突破,使得矽半導體材料也能電激發光,我們實驗室已經在實際的實驗中得到
此突破。突破的機制包含有以下可能性, (一) 利用粗糙面對電子物質波的繞射效
應,提供導電帶與價電帶放射性復合所需的動量,以滿足動量守恆的要求;(二)由
聲子輔助的放射性復合,復合所需的額外動量由聲子提供;(三)由激子(exciton,
electron-hole pair 的形成)的輔助,使聲子參與的機率增加;(四)利用具發光之奈米
粒子於矽晶片上,以取代矽之發光。我們希望透過此計畫,深入探討矽基材料電激
發光的物理機制和條件,並做出此類發光元件,以及研究提高電激發光效率的技術。
此外我們也希望藉由瞭解提高電激發光效率的機制,進一步探討這些機制是否也能
增強光電轉換效率,使矽基太陽電池的效率獲得進一步的改
Abstract: The electronics industry is the most important industry both in the world and in Taiwan
nowadays. On the other hand, the optoelectronics industry is also fast developing and will
soon become as important as electronics industry. Both industries rely on semiconductor
materials very much. However, electronics industry mostly uses Si, which is an indirect
bandgap material, while optoelectronics mainly uses direct-bandgap semiconductors. The
difference of materials makes the monolithic integration of products in both industries very
difficult. If both industries use the same type of materials, then their combination will
certainly have much more impact on the 21st century. Due to the maturity and cheap
fabrication cost of Si processing technology, it is unlikely that electronics will change the
major material –Si to another. This indicates that using indirect-bandgap materials for
optoelectronics will be the key issue for merging optoelectronics and electronics. The crucial
part will be the possibility of electroluminescence on indirect-bandgap materials like Si. In
addition, the speed of IC chips continues to increase, but the data transfer through the metal
wires is limited to around several GHz. Thus it has been long known that the break through
on the speed limitation of data transfer relies on the optical interconnect. Unfortunately, the
indirect-bandgap nature of Si material makes the light emission from IC chips and so optical
interconnect difficult. The possibility of electroluminescence from indirect-bandgap
materials like Si again provides the promise of optical interconnect for fast data transfer.
However, is it possible to make indirect-bandgap materials to emit electroluminescence? In
the past, the answer is negative. However, the fast progress of semiconductor technology, the
obstacle could be overcome so that electroluminescence from Si is possible. The physical
reasons for the possibility are hidden in the following factors. (1) If the crystal has certain
roughness patterns, the wavefunction of electrons might be properly disturbed to provide
extra momentum for electron-hole radiative recombination. (2) Phonon-assisted
electron-hole radiative recombination. The additional momentum required for momentum
conservation is provided by the phonon. (3) The formation of exciton by electron-hole pair
increases the probability of phonon involvement. (4) Use light-emitting nanoparticles on Si
wafers, so Si is not the light emission material. In our previous theoretical and experimental
study, we had found electroluminescence from Si material, so the possibility is positive.
Therefore, this project is proposed to study the physics and conditions for
electroluminescence based on Si in detail. The goal is to develop the li
Keyword(s)
矽
氧化鋅
品質因數
回音廊
模共振模態
奈
米粒
子。
Silicon
zinc oxide
quality factor
whispering-gallery modes
nanoparticles。