It was shown to have a possibility of p-n junction formation by laser radiation in certain semiconductors: p-Si [1], p-CdTe [2], p-InSb [3, 4] as well as others. Mechanism of p-n junction formation by laser radiation is not clear until now. In the experiments we have used Ge single crystals of i-type at room temperature with size: 16.0 x 3.5 x 2.0 mm. Current-voltage characteristics were measured at room temperature. Samples were treated with H2O2 in order to obtain minimum surface recombination velocity (S), which can be Smin = 100 cm/s. A permanent magnet with magnetic field of Bz=0.2 T was used in the experiments. Maximum electric field applied to the samples was Ex = 100 V/cm. Current-voltage characteristics in absence of magnetic field were linear, however when magnetic field was applied to the sample current-voltage characteristics were measured to be sublinear due to Magnetoresistance effect. Current-voltage characteristic of sample with asymmetrically treated opposite surfaces was diode type, due to Welker effect [5]. Asymmetry was obtained by mechanically polishing to obtain Smax -> ∞ and opposite surface was chemically treated to provide Smin. Surface of the sample with Smin was irradiated by fourth harmonic (λ = 266 nm, τ = 3 ns) of Nd:YAG laser. After irradiation by laser current-voltage characteristic became more diodic. We explain this phenomenon by p-n junction formation at the irradiated surface of sample. We have proposed a mechanism for this phenomenon by using Thermogradient effect [6], which causes redistribution of intrinsic defects, vacancies and interstitial atoms in temperature gradient field. Redistribution takes place because interstitial atoms’ drift towards the irradiated surface, but vacancies drift to the opposite direction – in the bulk of semiconductor. P-n junction is formed from interstitial Ge atoms being p-type and vacancies are known to be n-type.