It is interesting to see that all these wafers show anisotropy in mobility. The measured mobility difference in both direction on W0436 is shown in Fig. 7. This had been observed by many researchers ,  and . This could result from a number of reasons such as interface roughness, indium concentration modulation or anisotropic ordering appeared in the structures. In this TH588 work, the mobility anisotropy appears to follow the surface morphology anisotropy: the higher mobility is along [11¯0] which has larger undulation period. To verify the factors that account for hair shaft phenomenon, a more detailed study is required.
Fig. 7. Anisotropy of mobility in two different crystallographic directions at 1.5 K which is present at all gate voltages.Figure optionsDownload full-size imageDownload as PowerPoint slide
AcknowledgementThis work was funded by EPSRC Grant. One of the authors (C.Chen) would like to thank China Scholarship Council (CSC) for financial support.