In order to reduce the long diffusion times used in the production of power-semiconductor devices, two different methods of rapid thermal processing for the doping of Si with Al have been developed (Al-diffusion in a halogen lamp RTP-system and Al-doping via formation of Al-Si eutectic and epitaxial regrowth in a resistive graphite-heater RTP-reactor). Dopant profiles were characterized by SIMS- and SRP-analysis. In the case of Al-alloyed pn-junctions the quality of the recrystallized surface, as well as the shape and flatness of the junction, were investigated. Finally the minority-carrier lifetime of the bulk material after the diffusion process and the reverse blocking characteristics of the resulting junctions were determined. It is shown that rapid thermal processing is well suited to produce pn-junctions with blocking voltages beyond 2.5 kV. The dopant profiles of the diffused samples exhibit no indications for Al- or Al 2 O 3 -precipitates and junction depths are found to be between 1.4 and 3.2 μm. Charge-carrier lifetimes up to 250 μs after Al-predeposition have been obtained. The eutectic-doping process provides abruptpn -junctions with very high Al-concentrations (> 10 2 5 m - 3 ) and comparatively large junction depths (7.5 μm) at a maximum process temperature of 1320 K for only 10 s. Under suitable conditions it is possible to obtain a smooth recrystallized surface (roughness R a = 15 nm) and a uniform pn-junction without junction spiking.