P and B atomic layer doping has been achieved using LP(RT)CVD between room temperature and 400 degrees C. In the case of P doping, the process is self-limiting. P doses below one monolayer were deposited by separating adsorption of PH, and deposition of SiGe. Below 400 degrees C the dominating process is dissociative adsorption of PH, with an activation energy of 0.3 eV. At higher temperatures desorption of P decreases the incorporated P dose. For this reason, the temperature for P atomic layer doping should be below 550 degrees C to control the process by adsorption only. The P dose incorporated into SiGe may be controlled by the partial pressure of phosphine and by the hydrogen partial pressure. For B atomic layer doping, we find no self-limitation of the diborane adsorption. At low diborane partial pressures it is possible to prepare B peaks with a concentration below one monolayer. In this case the doping is dominated by the dissociative adsorption of diborane at Si and Ge surface sites. Using high partial pressures of diborane, several monolayers of B can be deposited. The diborane is adsorbed at B occupied surface sites. The results indicate atomic control of P and B at very low temperatures, which is important for decreasing the vertical dimensions of electronic devices.