The spectral dependences of surface photo-voltage and of intrinsic photoconductivity are analyzed for a quasi-monopolar semiconductor in the case of flat bands near the surface and taking into account the surface trapping. A method is developed for determining the diffusion length of minority carriers from the photo-voltage spectrum under such conditions and a method for determining the surface recombination velocities from the photoconductivity spectrum. The surface recombination velocity in GaAs epitaxial films is measured for different states of the surface: the natural growth surface and the surface after etching, after bombardment by argon ions, or after metallization. Experimental proofs of minority carrier trapping on the GaAs film surface are given. npOaHaJIEl3BpOBaHbI CIleKTpaJlbHhIe 3aBKCUMOCTH IIOBepXHOCTOfi @OT0-3RC CI CV6CTBeHHVii ~OTOnpOBOnHMOCTCI KBa3IIMOHOrlOJlfIPHO~O IlOnynpOBOnHHKa C nJIOC-KBMII 3OHaMB y nOBepXHOCTI4 EI C YseTOM ~OBe~XHOCTAOrO npHJIHnaHBf1. O6ocno-BaH MeTOA OIlpeHeJIeHHH HH@$Y3HOHHOfi jI,JIKHbI HeOCHOBHbIX HOCHTeneB TOHa IlO IlOBepXHOCTHOfi peKOM6CIHal1UCI no CIIeKTpy @OTOllpOBO~KMOCT~. fi3MepeHa CKOp O C T b IlOBepXHOCTHOfi peKOM6BHaUHCI B 3IlUTaKCHaJlbHbIX nJleHKaX n-GaAs npCI ~)a3JlKWtbIX COCTORHKRX IIOBepXHOCTCI : eCTeCTBeHIIaR IIOBepXHOCTb . POCTa, TpaB-JleHaH, 6OM6apJ(HpOBaHHaH KOHaMEi aprOHa II MeTanJlH3HpOBaHHaR IIOBepXHOCTR. nII)EiBOjI,HTCR 3KCnepIIMeHTaJTbHbIe AOHa3aTeJIbCTBa IlpHJlUIlaHUH HeOCHOBHbIX HO-cirercTpy QOTO-B~C B Tamx y c n o s~s x , a Taime MeTojI, onpeneneHHs c r r o p o c~~ cmeneii r-Ia r1osepxHocTI.r nxeHoK apcemna r a n a m .