探究GSMBE制备GaAsBi薄膜中生长条件对Bi浓度的影响

Influence of Growth Conditions on Bi Concentration in GaAsBi Thin Films Grown by GSMBE

为了探究GaAsBi薄膜生长中生长条件与Bi浓度的关系,我们利用气态源分子束外延(GSMBE)技术,通过改变每个GaAsBi单层的生长温度、AsH_3压和Bi源温度,在半绝缘GaAs(100)衬底上生长GaAsBi的多层结构。通过二次离子质谱(SIMS)及透射电镜X光谱(EDX)测试得出:GaAsBi中Bi的浓度随着生长温度的升高而降低,且生长速率越慢表面偏析和再蒸发严重,可导致Bi浓度下降趋势更明显;Bi浓度随着AsH_3压的升高而减小,在As_2和Ga束流比在0.5~0.8之间几乎成线性变化,远不如固态源MBE敏感;此外,Bi源温度升高,Bi掺入的浓度也会增大,但是当生长温度大于420℃时,Bi就很难凝入。

To explore the influence of growth conditions on Bi concentration,GaAsBi multilayer structured samples were grown on semi-insulating GaAs（100） substrates using gas source molecular beam epitaxy（GSMBE）.GSMBE growth parameters in terms of growth temperature,AsH3 pressure and Bi cell temperature were varied for each GaAsBi layer.Through secondary ion mass spectrometry and energy dispersive X-ray spectrum in transmission electron microscope,it is shown that Bi concentration decreases with increasing growth temperature.Under low growth rate,Bi concentration descends quickly with severe surface segregation and regasification.When As2：Ga flux ratio is between 0.5 to 0.8,Bi concentration changes linearly with AsH3 pressure,which is less sensitive than GaAsBi grown by solid source MBE.In addition,increasing Bi cell temperature enhances Bi incorporation reaching a saturation value at high growth temperatures.