We show that creation of a p-n junction in p-Si and p-InSb involve so-called donor laser centres (LCs). Analysis of our experimental data and other authors on p-n junction formation in p-InSb and p-Si using of laser radiation (LR) allowed us to conclude that a thermogradient effect plays the main role in this process. The following methods have been used in experiments: four-probe method and magnetoconcentration effect (MCE) (I-V characteristics in an external perpendicular magnetic field). A temperature gradient was created by YAG:Nd laser in the Q-modulation regime. Experiments on p-Si have shown that the LCs are n-type and they are created in materials doped with B and O only. Three types of LC were found: one type is stable at room temperature and two types are unstable. The effect of LC accumulation and saturation takes place in Si. The calculated distribution of O atoms in temperature gradient field and experiment are in qualitative agreement. Experiments on p-InSb have been carried out at 200 and 290 K. Generation of stable and unstable LC at room temperature was shown. Threshold intensities of LC generation are 1.5 MW/cm(2) at 200 C and 2 MW/cm(2) at 290 C. We conclude that generation of LC occurs in solid state. (C) 2002 Elsevier Science B.V All rights reserved.