Build-up processes of small-signal photo-emf and space-charge layer capacitance following cooling of the structure are investigated as well as the effect on them of fixed charge in the oxide and length of exposure to a voltage applied to the structure. It is shown that there are two types of recombination centers in the semiconductor which differ in the dependences of the concentrations and build-up times on the applied voltage. The centers of the first type determine the carrier recombination velocity in the weak inversion region, while centers of the second type are deep acceptors operating in the region of strong surface inversion. The latter are produced in the structure in the presence of an electric field. It is assumed that the recombinations centers originate from structural defects in the semiconductor and at the interface, whereby centers of the second type include indium vacancy and hydrogen. A mechanism of their emergence is proposed.