High Mobility HgTe Quantum Dot Films with Small Energy and Dynamic Disorder

The transport properties of HgTe colloidal quantum dot films are studied from 4 to 300 K with larger and more monodispersed quantum dots than previously. With nanocrystals of 14 nm diameter and 6.5% size distribution, a peak mobility of 65 cm2/(V s) is measured at 65 K for state-resolved transport in the 1Se state. Above 70 K, the mobility is band-like, but it follows the Marcus electron hopping model, while being far below the Mott–Ioffe–Regel limit. At 65 K, the average hopping time is as fast as 1 ps and getting close to the estimated dephasing time, or dynamic disorder, of the 1Se state, suggesting that coherence may exist for some neighboring dots. At lower temperatures, the mobility decreases for low bias, but it is temperature-independent for high bias due to field-driven transport. The Efros–Shklovskii variable range hopping model gives localization lengths of ∼100 nm, also suggesting large coherent domains. Twice lower mobility and shorter localization lengths are obtained with a 10 μm channel compared to a 2 μm channel, suggesting a possible percolation of the more conducting domains.