The hole concentration and strain relaxation of ultrathin GaMnAs film

Abstract

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.