  We study the disorder effect on the transport properties in the HgTe/CdTe
semiconductor quantum wells. We confirm that at a moderate disorder strength,
the initially un-quantized two terminal conductance becomes quantized, and the
system makes a transition to the novel topological Anderson insulator (TAI).
Conductances calculated for the stripe and cylinder samples reveal the
topological feature of TAI and supports the idea that the helical edge states
may cause the anomalous quantized plateaus. The influence of disorder is
studied by calculating the distributions of local currents. Base on the
above-mentioned picture, the phenomena induced by disorder in the quantum spin
Hall region and TAI region are directly explained. Our study of the local
current configurations shed further light on the mechanism of the anomalous
plateau.
