Abstract
An InAlAs/InGaAs resonant tunnelling structure was used to investigate the damage induced during thermal treatments of Au:Ge-based Ohmic contacts. The long-range coherence required for the observation of negative differential resistance was affected by all anneals at temperatures greater than 200 degrees C for times up to 120 s. The decrease in the sheet resistivity was correlated with the degradation of the tunnelling diode characteristics. Lateral spreading of the Ohmic metal was observed along the (110) and (100) directions for anneals at temperatures above 370 degrees C.