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The influence of surface state density NSS and bulk non-radiative lifetime t on room temperature photoluminescence quantum efficiency YPL and surface photovoltage (SPV) versus the excitation light intensity F was studied theoretically for GaAs and wurtzite GaN using self-consistent computer simulations. It was demonstrated that SPV(F ) dependences are more sensitive than YPL(F ) to a change in magnitude of NSS, especially for high NSS and at low F, whereas SPV is practically insensitive to t contrary to YPL. The simultaneous measurement of YPL and SPV versus F, combined with rigorous computer analysis, seems to be a very promising method for contactless characterization of the surface and bulk trap parameters.