用泵浦-探测方法研究ZnCdSe量子阱/CdSe量子点复合结构中的激子衰减

Exciton Decay in ZnCdSe QW/CdSe QD Using Femtosecond Pump-probe Measurement

用飞秒泵浦－探测方法测量了ＺｎＣｄｓｅ量子阱／ＺｎＳｅ／ＣｄＳｅ量子点复合结构样品的透射特性。样品中ＺｎＳｅ垒层厚度为 １５ｎｍ，泵浦一探测结果得到上升沿时间为 ３６７±６０ｆｓ，下降沿时间为１．３±０．２ｐｓ。获得ＺｎＣｄＳｅ量子阱中激子寿命约为１ｐｓ。

The transmission intensity of ZnCdSe quantum well / CdSe quantum dot combination structure vs delay time is investigated using femto-second pump-probe measurement. Femto-second pulse with pulse width 130fs and wavelength 537um utilized as pump and probe pulse in the pump-probe measurement is yielded using locking mode Ti: sappire femto-second laser (Spectra-physics laser Co. ) and tuned by OPA-800. The transmission intensity of probe pulse vs the delay time between pump pulse and probe pulse is detected using multiplier phototube. The structure of experimental sample is ZnSe buffer / 7um ZnCdSe(QW) / 15um ZnSe barrier / 10um CdSe (QD)/ ZnSe. ZnSe, ZnCdSe and CdSe were grown on GaAs substrate by molecular beam epitaxy, and then the GaAs substrate is eroded by corrosive. The absorption peak of exciton in ZnCdSe quantum well of experimental sample is located at 528um. The transmission intensity characteristic with the delay time of probe pulse is shown in Fig. 4. On the basis of the condition of experiment, we consider the rise-time of turn-on side is primarily determined by pump pulse lineshape and the down time of turn-off side is donated from exciton decay in ZnCdSe quantum well. Fitting the data of pump-probe experiment, the rising time of 367 ±60fs and the down-time of 1. 3±0. 2ps are obtained. Extracting the donation of pulse lineshape in down-time, the exciton decay time is 1ps calculated from turn - off side of the pump-probe transmission curve.