利用飞秒双光子光电子发射研究GaAs(100)的自旋动力学过程

超短激光技术的发展为研究材料中的超快光动方学过程提供了重要的实验手段，也使得人们 能够更为深入地研究电子的自旋动力学行为.GaAs(100)表面由于费米钉扎而会导致能带弯曲 ，位于该区域的电子及其自旋特性将会明显不同于体相材料中的情况.利用时间分辨和自旋 分辨的双光子光电子发射技术研究了p型掺杂GaAs(100)表面的电子极化动力学过程.结果表 明，由费米钉扎而引起的能带弯曲明显影响电子的自旋弛豫过程，从实验上观察到了GaAs(1 00)表面能带弯曲区域的电子自旋翻转时间存在近2个量级的差异(从几纳秒到几十皮秒)，基 于电子-自旋交换相互作用的BAP机理在自旋弛豫过程中起着主导作用. 关键词： 光物理 自旋极化 双光子光电子发射 砷化镓

Spin dynamics of GaAs(100) by two-photon photoemission

On p-doped GaAs(100) surface, the band bending arising from Fermi-level pinning significantly affects the carrier and spin dynamics. In this paper, we report th e dynamics of spin polarization of p-doped GaAs(100) by using the time-resolve d and the energy-resolved two-photon photoemission techniques. By measuring the spin and energy relaxation of electrons emitted from the GaAs(100) surfaces, th e dynamics of spin polarization were observed and the mechanism of spin relaxati on was discussed as well. The experimental measurements together with the theore tical results indicate that the Bir-Aronov-Pikus (BAP) mechanism plays a dominan t role for spin polarization decay, especially in band bending region of GaAs(10 0).