Piezoelectric photoacoustic spectroscopy with a piezoelectric detection has been used for measurements of the amplitude and phase spectra of Zn1-x-yBexMnySe mixed semiconductors. The investigated crystals were grown from the melt by the modified high pressure Bridgman method under the argon overpressure. The preliminary study of the sample's surface of the investigated crystals was carried out using the AFM technique. The influence of a different surface treatment on the amplitude and phase piezoelectric spectra as well as on AFM images is presented and analyzed. The correlations between these two techniques have been found and are discussed. Piezoelectric (PZE) spectra were analyzed using an extended and modified Jackson-Amer theory. (C) 2013 Elsevier B.V. All rights reserved.