Inter-layer subb and mixing in MBE-grown HgTe/CdTe superlattices
We report transport results for molecular beam epitaxially grown HgTe/CdTe superlattices (SLs) with CdTe barrier thickness of Lb systematically varied from 100Å down to 20Å, and demonstrate the increasing intersubband mixing between adjacent layers with decreasing Lb. Magnetotransport data measured at 1.5K and for B up to 10T show monotonously varying features with Lb, implying a dimensional change from 2D to quasi-3D. As Lb decreases, the quantum Hall plateaus become weaker and the number of effective 2D channels are decreased, which indicates increasing growth-direction energy dispersion. This enhanced interlayer subband coupling with decreasing Lb is further confirmed by the angle-dependence of SdH oscillations. For Lb = 20Å, all of 2D-related transport behavior are washed out. A quantitative analysis with calculated subband energy dispersion relations demonstrates the close interplay between superlattice barrier thickness and the strength of the intersubband mixing. These transport results are directly related to successful control of the growth-axis carrier effective mass and will contribute to the development of high-performance HgTe/CdTe SL-based IR photo-voltaic devices and lasers, in which tunneling noise due to diffusion currents can be considerably reduced.