Infrared photothermal radiometric deep-level transient spectroscopy (PTR-DLTS) has been applied to noncontact diagnostics of ap-Si wafer. Both negative and positive peaks in the PTR-DLTS signal temperature scans have been detected. A behavior consistent with photoinjected carrier lifetime enhancement due to the thermal filling ofB+dopant levels in the band gap has been observed. The activation energies of 43 meV (negative peaks) and 60 meV (positive peaks) have been extracted from the corresponding Arrhenius plots. ©1997 American Institute of Physics.