Ultrahigh vacuum surface studies of the electrochemical atomic layer deposition of indium telluride on n-type GaAs(100)
The electrodeposition of tellurium (Te) and indium (In) atomic layers on n-type GaAs(100) substrates is described. As-received n-GaAs(100) substrates were treated in 10% HF and ultraviolet (UV) ozone cleaned. The substrates were then transferred to an ultrahigh vacuum (UHV) chamber and cleaned by Ar+ ion bombardment. The clean substrate was then transferred into an attached electrochemistry ante-chamber and immersed in a telluride solution, where a number of deposition potentials were investigated. The resulting Auger peak height ratios, Te/Ga, were plotted versus the Te deposition potential. From the Auger ratios, it was evident that bulk Te was formed between -0.4 and -0.8 V, while below -0.8 V, a reduction feature was observed corresponding to the reduction of Te to the telluride ion (Te-0 + 2e(-) - Te2-). Below -0.9 V, only a surface-limited atomic layer of Te was left on the GaAs surface. Indium deposition on this Te-coated GaAs surface was also performed, and electrodeposited adlayer thicknesses were calculated from the Auger data. Indium electrodeposited directly on the GaAs surface resulted in 3D nucleation and growth of widely spaced In clusters. Electrodeposition of In on an atomic layer of Te on the GaAs surface resulted in layer-by-layer growth. Alternation of atomic layers of Te and In resulted in formation of indium telluride nanofilms, probably In2Te3, by electrochemical atomic layer deposition (ALD). Deposits with up to three cycles were performed.