In this work we present the results of an investigation into the effectiveness of varying (NH4)2S concentrations in the passivation of n-type and p-type In0.53Ga0.47As, as determined through analysis of electrical properties. Samples were degreased and immersed in aqueous (NH4)2S solutions of concentrations 22%, 10%, 5%, or 1% for 20 minutes at 295K, immediately prior to ALD growth. Capacitance-voltage results on capacitor structures indicate that the lowest frequency dispersion over the bias range examined occurs for n and p-type devices treated in 10% (NH4)2S solution. The deleterious effect on interface state density of increased ambient exposure time after removal from (NH4)2S solution is also presented. Estimations of peak interface state density, Dit, extracted from the equivalent parallel conductance Gp, using an approximation to the conductance method, are used for comparison of the different passivation conditions.