UV detectors with integrated amplification
The detection of blue and ultraviolet (UV) light is of interest in numerous applications. In particular, very low-light effects, such as fluorescence analysis of medical or biological samples, pose a special challenge because the spectral sensitivity of established silicon pn or pin photodiodes is relatively low in this range. An established technology for very small light signals are so-called avalanche photo diodes (APD), in which an internal multiplication - i.e. an amplification - of the free charges generated by light is achieved by several, sometimes very highly doped zones in the silicon with high operating voltages of up to about 200 V. This technology has, however, so far not been used for blue light. Until now, however, this technology has not been optimally suited for blue and UV light, since such light is associated with very shallow penetration depths into the silicon at which the amplification effects of APD have little or no effect.
This is where the newly developed technology for blue- and violet-sensitive APD (BVAPD) comes in. Particularly shallow doping processes have been developed for this spectral range, where light penetrates the silicon only a few micrometers or even only a few 100 nm deep. The amplifying zones within the APD thus shift to regions closer to the surface of the silicon detector, significantly increasing its sensitivity. This effect is illustrated by the results of the first demonstrators: in the blue spectral region, an amplification of the output signals by a factor of more than 100 could be achieved. Spectral amplification also shows that this technology achieves the desired high sensitivity for wavelengths from 400 nm and below.
The technologies and demonstrators developed within a funded project (BVAPD, 49MF200098, InnoKom) are now available for the development and fabrication of application and customer specific detectors.