Piezoreflectance Study of GaAs/AlGaAs Digital Alloy Composi-

• Main Authors: F.C.Lin, 林峰全
• Other Authors: Y.S.Huang
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/35621026742954389455

碩士 === 國立臺灣科技大學 === 工程技術研究所 === 83 === We have studied the piezoreflectance (PzR) spectra from 20K to 300K related to the intersubband transitions from four (001) GaAs/AlGaAs structures fabricated by molecular beam epitaxy using the digital alloy compositional grading (DACG) method. These samples include an asymmetric triangular quantum well (ATQW) and three rectangular quantum wells(RQW) with different unit cells [ 50A(x2);25A(x4) and 12.5A(x8)]. A comparison of the relative intensity of heavy- and light-hole related features in the PzR spectra and those in the photo- reflectance emphasizes the contribution of the strain dependence of the energies of the confined state which allows us to identify the features associated with the heavy- and light-hole valence bands unambiguously. For the ATQW comparison of the observed intersubband resonances with a theoretical calculation (envelope function method) provided a self-consistent verification that the DACG produced the intended result,i.e., an effective linearly graded profile. For the RQW materials the 12.5A unit cell sample essentially had the characteristics of the intended analog configuration while the other two samples displayed observable differences.