Experimental investigation of Hall mobility in Ge/Si quantum dot superlattices

Abstract

We report results of measurements of Hall mobility in a set of doped and undoped GexSi1−x/Si quantum dot superlattices (x=0.50 and 0.73). The dome-shaped Ge quantum dots have the characteristic base size of 40 nm and height of about 4 nm. The molecular beam epitaxy grown structures consist of 5–20 layers of Ge quantum dots separated by 20-nm-thick Si layers. The position of δ doping varies for different samples. The average measured in-plane Hall mobility for p-type structures is 140 cm2 V−1 s−1 at 300 K and 2.4×103 cm2 V−1 s−1 at 77 K. Relatively large values and temperature dependence suggest that in given quantum dot structures the carrier transport is likely of the band conduction type rather than hopping type. These results are important for proposed optoelectronic and thermoelectric application of quantum dot superlattices.