Carrier dynamics in GaAs/AlAs ridge quantum wire

用光学方法研究了砷化镓/砷化镓脊量子线中的载流子动力学。我们只能进行荧光光谱及其寿命的测量。[实验]利用Ti:Sapphire再生放大器飞秒输出脉冲（λ=400nm, 100μJ, 150fs）的SHG作为激发。本文研究的样品分别为A1458 （AlAs 10nm-GaAs 7nm-AlAs 3nm）、A1472 （AlAs 5nm- al_ <0.5>Ga_<0.5>As 170nm-GaAs 6nm-Al_<0.5>Ga_<0.5>As 170nm-AlAs 5nm）、A1480 （AlAs 3nm- al_ <0.3>Ga_<0.7>As 283nm-GaAs 6nm-AlAs 3nm）和具有相同层状结构的脊量子线。利用条纹相机对样品（10K）的荧光进行寿命测量。【实验结果】(1)GaAs/AlAs量子阱的寿命测量在强激发的情况下，我们观察到较宽的荧光光谱。这可能是由于量子阱中的最低激发态由于激发态载流子的高密度而饱和所致。在这种情况下，波长越短，寿命越短。在弱激发的情况下，我们观察到量子阱中出口的窄谱。测量的寿命分别为1290ps（A1458）、427ps（A1472）和280ps（A1480）。在样品A1480中，还观察到屏障（Al_<0.3>Ga_<0.7>As）在666 nm处的荧光。(2) GaAs/AlAs脊量子线的寿命测量我们测量了A1480脊样品的荧光寿命。在678和725 nm处观察到两个荧光峰。在660 nm波长处，荧光寿命很短，而在680 nm波长处，荧光寿命相对较长。在700 nm处，荧光表现为双指数衰减，在720 nm处变为单指数衰减。在740 nm处，寿命再次延长。基于这些测量，我们将678 nm和725 nm处的荧光峰分别归因于侧qw和QWR。

We have investigated the carrier dynamics in the GaAs/AlAs ridge quantum wire by the optical methods. We could solely perform the measurement of the fluorescence spectra and its lifetime.[Experimental]We used the SHG of the femtosecond output pulse from a Ti:Sapphire regenerative Amp. (λ=400nm, 100μJ, 150fs) as the excitation. The samples studied here were the quantum wells, A1458 (AlAs 10nm-GaAs 7nm-AlAs 3nm), A1472 (AlAs 5nm-Al_<0.5>Ga_<0.5>As 170nm-GaAs 6nm-Al_<0.5>Ga_<0.5>As 170nm-AlAs 5nm), A1480 (AlAs 3nm-Al_<0.3>Ga_<0.7>As 283nm-GaAs 6nm-AlAs 3nm) and the ridge quantum wire with the same layer structure. The lifetime measurement of the fluorescence from the sample (10K) was carried out by using a streak camera.[Experimental Results](1) Lifetime measurement in GaAs/AlAs quantum wellsIn the case of strong excitation, we observed the broad fluorescence spectrum. It probably results from that the lowest excited states in quantum well are saturated due to the high density of the excited carriers. In this case, the lifetime was shorter at the shorter wavelength. In the case of weak excitation, we observed the narrow spectrum from the extitons in the quantum well. The measured lifetimes were 1290ps(A1458), 427ps(A1472), 280ps(A1480), respectively. In the sample A1480, the fluorescence at 666 nm of the barrier (Al_<0.3>Ga_<0.7>As) was also observed.(2) Lifetime measurement in GaAs/AlAs ridge quantum wireWe measured the lifetime of fluorescence in A1480 ridge sample. Two peaks were observed at 678 and 725 nm in the fluorescence spectrum. The lifetime of fluorescence was measured to be very short for the wavelength of 660 nm, but to become relatively long at 680 nm. At 700 nm, the fluorescence showed the two-exponential decay and it became the single-exponential deay at 720 nm. At 740 nm, the lifetime was observed to be long again. Based on these measurement, we attribute the fluorescence peaks at 678 nm and 725 nm to side-QW and QWR, respectively.