超薄GaMnAs外延膜空穴浓度和应变弛豫研究

The hole concentration and strain relaxation of ultrathin GaMnAs film

稀磁GaMnAs外延膜中的Mn含量会影响外延膜的空穴浓度和应变弛豫.Raman散射研究表明,Mn含量为3%的超薄GaMnAs样品的空穴浓度大于2%样品,4%样品的空穴浓度小于3%样品.应变弛豫理论和高分辨X射线衍射研究表明,Mn含量为2%和3%的超薄GaMnAs外延层分别处于准共格或低弛豫状态,Mn含量为4%的GaMnAs外延层的弛豫度明显大于3%样品的弛豫度.我们认为,准共格或低弛豫度状态对空穴浓度随Mn含量的变化趋势几乎没有影响,较大弛豫度的应变状态将导致样品外延层产生较多缺陷,影响能带结构和能级,引起空穴浓度异常减小.

The hole concentration and strain relaxation degree in the diluted magnetic epitaxial film of GaMnAs are affected by the Mn concentration. The result from Raman scattering spectrum experiment has shown that the hole concentration in ultra-thin GaMnAs sample with Mn concentration of 3% is greater than that in sample with Mn concentration of 2%,while the hole concentration in sample with Mn concentration of 4% is less than that in sample with Mn concentration of 3% . Based on the theory of strain relaxation and investigation by HRXRD,it was indicated the samples with Mn concentration of 2% and 3% are in quasi-coherence or with low relaxation degree,respectively. On the other hand,the sample with Mn concentration of 4% obviously has a greater relaxation degree than that with 3% concentration. Therefore,it is suspected that the status of quasi-coherence or low relaxation degree hardly affects the hole concentration with the change of the Mn concentration. However,the strain relaxation status of large relaxation degree results in more defects in the epitaxial layer which affects the energy band and level thus decreases the hole concentration dramatically.