Localization of trivial edge states in InAs/GaSb composite quantum wells

The InAs/GaSb heterostructure is one of the systems where the quantum spin Hall effect is predicted to arise. However, as confirmed by recent experimental studies, the most significant highlight of the effect, i.e., conductance quantization due to nontrivial edge states, is obscured by spurious conductivity arising from trivial edge states. In this Rapid Communication, we present an experimental observation of the strong localization of trivial edge modes in an InAs/GaSb heterostructure which was weakly disordered by silicon deltalike dopants within the InAs layer. The edge conduction which is characterized by a temperature-independent behavior at low temperatures and a power law at high temperatures is observed to be exponentially scaled with the length of the edge. Comprehensive analyses on measurements with a range of devices is in agreement with the localization theories in quasi-one-dimensional electronic systems.