摘要
我們以光調制反射光譜(PR)來研究由MOCVD長成的GaAs/GaNxAs1-x 多量子井結構(MQW)。實驗結果發現能量在GaAs能隙以上的譜形，有兩組FKO振盪譜形，而能量在GaAs能隙以下的譜形是GaNxAs1-x能隙與GaAs/GaNxAs1-x量子井躍遷所產生的訊號，藉由分析FKO振盪譜形，可以推算樣品的內建電場。
當GaNxAs1-x /GaAs 多量子井能帶的排列方式為type-Ⅰ型且能帶落差Qc:Qv=8.8:1.2時，最能符合譜形的躍遷訊號，此外，藉由量子井躍遷的能階，來分析在不同N含量下，GaNxAs1-x電子的有效質量：當N含量分別為0.9% 與4%時，GaNxAs1-x電子的有效質量為0.08m0與0.41m0。

Photoreflectance Research of GaAs/GaNxAs1-x
Quantum Wells Structure
ABSTRACT
We have studied the GaAs /GaNxAs1-x multiple quantum wells grown by Metal-Organic Chemical Vapor Deposition using photoreflectance at various temperatures and nitrogen contents . The photoreflectance spectral features above the energy gap of GaAs include two sets of Franz-Keldish oscillations ,and features
below the energy gap of GaAs are the GaNAs energy gap transtion and the quantum well excitionic interband transtions . By the analysis of the line shapes of the Franz-Keldish oscillations , we obtained the built-in electric fields of the sample .
The interband transition energies for multiple quantum wells with different nitrogen contents and well widths can be well fitted if a type -Ⅰband line up of GaAs/GaNxAs1-x multiple quantum wells and band offsets with Qc:Qv=8.8:1.2 are assumed . Furthermore , we are able to determine the electron effective mass for GaNxAs1-x as a function of x . The electron effective masses are =0.08mo and 0.41mo with N composition of 0.9% and 4.0% ,respectively.

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