A semiconductor processing technique is disclosed for forming a multi-layered semiconductor structure in a single chamber and with the same equipment, without removing the semiconductor wafer substrate or otherwise transferring it to another chamber. A gaseous mixture of different gases is provided in a chamber. Excimer pulsed ultraviolet laser radiation is introduced into the chamber at a first discrete wavelength to photolytically react with a first of the gases at a discrete excitation energy photochemically breaking bonds of the first gas to epitaxially deposit a first layer on the substrate, followed by radiation at a second discrete wavelength to photolytically react with a second gas to deposit a second layer on the first layer, and so on. The different gases may be introduced into the chamber collectively, or serially between radiations. Scavenging between layers is provided by photolytic removal of surface containments and the products of reaction.