臺灣博碩士論文加值系統

本文主要是探討半導體二維電子氣(Two dimension electron gas ;
2DEG)和超晶格(superlattice)的電子特性,首先介紹一種計算能帶結構的
方法:最緊束鍵結法(tight-binding),以sp3s*模型計算I型半導體GaAs/
AlAs超晶格能帶結構,和不同厚度直接(direct)-間接(indirect)能隙的轉
換,作為分析實驗的基礎.再來進入主題半導體二維電子氣的實驗,主要是
探討AlGaSb/InAs量子井(quantum well)在1.5K下隨磁場改變
(0-12Tesla)的電子特性,使用的方法是 Shubnikov-de Haas (SdH)測量
和 Quantum Hall effect (QHE)測量,並且比較在低溫(1.5K)照光(red
LED;635nm)前後,發現有負持續性光導效應(Negative persistent photo-
conductivity effect; NPPC effect),在InAs well的電子密度因負持續
性光導效應而減少.

The main purpose of this thesis is to explore the properties of
electrons in the two-dimension electron gas(2DEG)and super-
lattice. In the firt part, we introduce a scheme of computing
the band structure:the tight-binding method,to comput that of
type-I GaAs/AlAs semi-conductor superlattice by the adoption of
sp3s* model,and the direct-indirect transitions between the
energy gaps of different thickness,as the theoretic groundwork
of our analyzing experiment.In the second part,the two-
dimension electron gas(2DEG)experiment.We next explore the
electrons properties in the quantum well of AlGaSb/InAs at low-
temperature 1.5K, which is varied with the external magnetic
field. We used Shubnikov-de Haas(SdH)measurements and Quantum
Hall effect(QHE) measurements as our experiment approach,and
found that there was a negative persistent photoconductivity(
NPPC)effect after the illumination(red LED;635nm)at low-
temperature(1.5K).By illuminat- ing the sample at low-
temperature,the carrier concentration of the two-dimension
electron gas in the InAs well was decreasing.