Formation of localised molten regions in silicon containing multiple impurity types

A method for creating an inwardly extending impurity distribution profile in a substrate comprising crystalline silicon material having a background doping of a first impurity type, comprising: a) providing one or more additional impurity sources with at least two different types of impurity atoms within the substrate or in proximity to the surface of the substrate, with each of these impurity atoms having different diffusion coefficients or segregation coefficients; b) locally melting a point on the surface of the substrate with a laser, whereby the at least two different types of impurity atoms are incorporated into the melted silicon material; c) removing the laser to allow the silicon material to recrystallize; d) controlling a rate of application and/or removal of the laser to control the creation of the impurity distribution profile, with different distribution profiles for each of the at least two types of impurity atoms in the recrystallized material.