A device manufacturing method, comprising the following steps: impregnating a silicon wafer with impurities that form one or more deep energy levels within the band gap of silicon, wherein at least one of said deep energy levels is positioned at least 0.3 eV away from the conduction band if the level is a donor level or at least 0.3 eV away from the valence band if the level is an acceptor level, the impregnating comprising diffusing the impurities, wherein the diffusing of the impurities is performed by depositing the impurities on a surface of the silicon wafer and leaving the impurities to diffuse into the bulk at elevated temperature or by using ion implantation to project the impurities into the silicon wafer followed by annealing, and wherein the concentration of the impurities after the impregnation is in the range of 10 13 to 10 18 cm -3; and forming a device layer comprising electronically functional components, characterised in that: the silicon wafer is pre-processed, prior to said impregnating step, so that precipitation of oxide during, after, or during and after, said impregnating step is suppressed, the pre-processing comprising removing the oxide clusters/nuclei to a level that is insufficient to give rise to significant precipitation in subsequent processing steps, by using a heat treatment to dissolve all or a proportion of oxide clusters/nuclei present before the pre-processing, the heat treatment comprising holding the silicon wafer at a temperature between 900 and 1250 degrees C for between 30 seconds and 60 minutes, followed by reducing the temperature of the silicon wafer to below 700 degrees C in less than 10 minutes. impregnating a silicon wafer with impurities that form one or more deep energy levels within the band gap of silicon, wherein at least one of said deep energy levels is positioned at least 0.3 eV away from the conduction band if the level is a donor level or at least 0.3 eV away from the valence band if the level is an acceptor level, the impregnating comprising diffusing the impurities, wherein the diffusing of the impurities is performed by depositing the impurities on a surface of the silicon wafer and leaving the impurities to diffuse into the bulk at elevated temperature or by using ion implantation to project the impurities into the silicon wafer followed by annealing, and wherein the concentration of the impurities after the impregnation is in the range of 10 13 to 10 18 cm -3; and forming a device layer comprising electronically functional components, characterised in that: the silicon wafer is pre-processed, prior to said impregnating step, so that precipitation of oxide during, after, or during and after, said impregnating step is suppressed, the pre-processing comprising removing the oxide clusters/nuclei to a level that is insufficient to give rise to significant precipitation in subsequent processing steps, by using a heat treatment to dissolve all or a proportion of oxide clusters/nuclei present before the pre-processing, the heat treatment comprising holding the silicon wafer at a temperature between 900 and 1250 degrees C for between 30 seconds and 60 minutes, followed by reducing the temperature of the silicon wafer to below 700 degrees C in less than 10 minutes. the silicon wafer is pre-processed, prior to said impregnating step, so that precipitation of oxide during, after, or during and after, said impregnating step is suppressed, the pre-processing comprising removing the oxide clusters/nuclei to a level that is insufficient to give rise to significant precipitation in subsequent processing steps, by using a heat treatment to dissolve all or a proportion of oxide clusters/nuclei present before the pre-processing, the heat treatment comprising holding the silicon wafer at a temperature between 900 and 1250 degrees C for between 30 seconds and 60 minutes, followed by reducing the temperature of the silicon wafer to below 700 degrees C in less than 10 minutes.