室温下(Ga,Mn)As中载流子的自旋弛豫特性

Carrier spin relaxation in (Ga,Mn)As at room temperature

运用飞秒时间分辨抽运-探测克尔光谱技术,研究了室温下退火及未退火(Ga,Mn)As的载流子自旋弛豫的激发能量密度依赖性,发现电子自旋弛豫时间随激发能量密度增加而增大,而在同一激发能量密度下,退火样品比未退火样品具有更短的载流子复合时间、电子自旋弛豫时间和更大的克尔转角,显示DP机理是室温下(Ga,Mn)As的电子自旋弛豫的主导机理.退火(Ga,Mn)As的超快克尔增强效应显示其在超高速全光自旋开关方面的潜在应用价值,也为(Ga,Mn)As铁磁性起源的p-d交换机理提供了证据.

In this paper, the excitation energy density dependence of carrier spin relaxation is studied at room temperature for the as-grown and annealed （Ga,Mn）As samples using femtosecond time-resolved pump-probe Kerr spectroscopy. It is found that spin relaxation lifetime of electrons lengthens with increasing excitation energy density for both samples, and the annealed （Ga,Mn）As has shorter carrier recombination and electron spin relaxation lifetimes as well as larger Kerr rotation angle than the as-grown （Ga,Mn）As under the same excitation condition, which shows that DP mechanism is dominant in the spin relaxation process for （Ga,Mn）As at room temperature. The enhanced ultrafast Kerr effect in the annealed （Ga,Mn）As shows the potential application of the annealed （Ga,Mn）As in ultrafast all-optical spin switches, and also provides a further evidence for the p-d exchange mechanism of the ferromagnetic origin of （Ga,Mn）As.