Comparison of Hole Effective Mass Between Various Biaxially Strained Ge Semiconductors

The directional, averaged, and density-of-states effective masses of hole in biaxially strained Ge were studied on the basis of the dispersion relation. We focus on their difference between the (001), (101) and (111) strained Ge. For the three type of strained Ge, the relations of the various hole effective mass between the stress are similar and their values are different. The results are described as follows: (1) The results of the directional mass of hole in strained Ge show that the anisotropy of valence band must be considered in developing an accurate hole transport model. (2) The results of the averaged effective mass corresponding to the first and second bands exhibit that the traditional concepts of heavy and light holes are still suitable. (3) The decreases in density-of-states and conductivity effective masses of hole with decreasing Ge fraction are found in strained Ge.