GaAs_(1-x)Sb_x/GaAs单量子阱的光学特性研究

Study of optical properties in GaAs_(1-x) Sb_x/GaAs single quantum wells

用选择激发光荧光研究了分子束外延生长的GaAsSb GaAs单量子阱的光学性质 ,第一次同时观察到空间直接(Ⅰ类 )和间接 (Ⅱ类 )跃迁 .它们表现出不同的特性 :Ⅰ类跃迁具有局域化特性 ,其发光能量不随激发光能量而变 ;Ⅱ类发光的能量位置随激发功率的增大而蓝移 ,也随激发光能量的增加而蓝移 ,复合发光发生在位于异质结GaAs一侧的电子和GaAsSb中的空穴之间 ,实验结果可以很好地用电荷分离造成的能带弯曲模型来解释 ,这也是空间间接跃迁的典型特性 .还用光荧光的激发强度关系和时间分辨光谱进一步论证了GaAsSb GaAs能带排列的Ⅱ类特性 ,并通过简单计算得到了应变和非应变状态下GaAsSb GaAs异质结的带阶系数 .

GaAsSb/GaAs single quantum wells (SQWs) grown by molecular beam epitaxy are studied by selectively excited photoluminescence (SEPL) measurement. For the first time, we have simultaneously observed the PL from both type Ⅰ and type Ⅱ transitions in GaAsSb/GaAs heterostructure in the SEPL. The two transitions exhibit different PL behaviours under different excitation energy. As expected, the peak energy of type I emission remains constant in the whole excitation energy range we used, while type Ⅱ transition shows a significant blue shift with increasing excitation energy.The observed blue shift is well explained in terms of electron hole charge separation model at the interface. Time resolved(TR) PL exhibits more type Ⅱ characteristic of GaAsSb/GaAs QW. Moreover, the results of the excitation power dependent PL and TRPL provide more direct information on the type Ⅱ nature of the band alignment in GaAsSb/GaAs quantum well structures. By combining the experimental results with some simple calculations, we have obtained the strained and unstrained valence band offsets of Q v=1 145 and Q 0 v=0 76 in our samples, respectively.