分子束外延GaAs/Si应变层的光致发光和光反射谱研究

Photoluminescence and Photoreflectance of GaAs on (100) Si Grown by Molecular Beam Epitaxy

研究了分子束外延GaAs/Si光致发光谱的激发强度和温度依赖关系。确定出2个本征发光峰,分别对应于导带至m_J=±3/2和m_J=±1/2价带的复合。这种价带的移动和分裂归因于由GaAs和Si的热膨胀系数不同所引起的GaAs层双轴张应力。还观测到4个非本征发光峰,分别为导带至m_J=±1/2碳受主态发光、可能与缺陷有关的发光以及可能由Mn和Cu受主杂质引起的发光。室温下将GaAs/Si和GaAs/GaAs材料的光反射谱进行比较,前者明显向低能移动约8meV,观测到3个特征谱结构,与光致发光结果相一致。

The photoluminescence of GaAs/Si grown by MBE has been analyzed as a function oftemperature and excitation density.Two peaks have been identified as the transitions of theconduction band to m_J=±3/2 and m_J=±1/2 valence bands, respectively The valence bandsplitting is due to the biaxial tensile stress in the GaAs layer at temperatures below thegrowth temperature. The stress is caused by the difference in thermal expansion coefficientsbetween GaAs and Si.Four extrinsic peaks are identified as the recombinations from the conductionband to carbon, Mn and Cu acceptors and a defect related emission band, respectively.The room temperature photoreflectance spectrum of GaAs/Si shifts to the lower energy comparedwith that of GaAs/GaAs material.Three structures are identified and in agreement with theresults of photoluminescence.