Formation of a ZnO/ZnS interface passivation layer on (NH4)2S treated In0.53Ga0.47As: Electrical and in-situ X-ray photoelectron spectroscopy characterization

Abstract

Atomic layer deposition is used to convert an (NH4)2S cleaned p-In0.53Ga0.47As with diethylzinc (DEZ) and water, resulting in the formation of a ZnO/ZnS interfacial passivation layer (IPL). The process is studied using in-situ X-ray photoelectron spectroscopy. DEZ reacts with sulfur and oxygen present on the surface, chemically reducing arsenic 3+ and gallium 3+ to lower oxidation states. The sulfur concentration remains constant during the deposition process while the oxygen concentration on the surface remains small, confirming that the IPL is composed of both ZnO and ZnS. Measurements of metal–oxide–semiconductor capacitors with HfO2 for the dielectric show that the ZnO/ZnS IPL can nearly eliminate frequency dispersion (<1% per frequency decade) in accumulation and results in small hysteresis (<60 mV) with a Dit in the 1011 eV−1 cm−2 range in the midgap. Frequency dispersion is observed in the depletion region and is attributed to minority carrier generation from the ZnO present in the IPL.