Optical sensor having two taps for photon-generated electrons of visible and IR light
An optical sensor in which photo currents generated by light in the visible and infrared wavelength ranges are to be tapped separately at pn junctions of active regions. The active regions include n- or p-doping and are formed in a p-substrate 52 . The optical sensor comprises a surface-near first active region 12 , and a second active region 14 subjacent to the first active region 12 and forming together with the first active region 12 a pn junction 22 that is short-circuited. A third active region 20 is subjacent to the second active region 14 and forming together with the second active region a further pn junction 23 . Together with a fourth active region 24 subjacent to the second active region 20 , a further pn junction 25, 29 is formed together with the third active region 20 and the substrate 52.
1. Optical sensor for providing photo currents generated by light in the visible wavelength range and light in the infrared wavelength range, tapped separately at pn junctions of active regions formed in a p-substrate ( 52 ), wherein the sensor comprises a plurality of stacked active regions ( 12 , 14 , 20 ) and a plurality of pn junctions ( 22 ; 23 ; 25 , 29 ), each one thereof provided between two adjacent active regions ( 12 , 14 ; 14 , 20 ; 20 , 24 ), and wherein:
one of the active regions is a p-doped surface-near active region ( 12 ) that comprises a high p+ doping that decreases in a depth of the optical sensor;
a further one of the active regions is formed below the surface-near active region ( 12 ) as a subjacent n-doped active region ( 14 ) having an n-doping that decreases in the depth of the optical sensor and forming a short-circuited pn junction ( 22 ) with the surface-near active region;
a further one of the active regions is formed as a p-doped active region ( 20 ) subjacent to the n-doped active region ( 14 ), which has a p-doping that decreases towards the n-doped active region ( 14 ) and which forms therewith a further pn junction ( 23 ), a photo current thereof produced by light in the visible wavelength range and tapped at a first cathode ( 18 );
a further one of the active regions is formed as an n-doped active region ( 24 ) subjacent to the p-doped active region ( 20 ) and having as a doping profile an n-doping that decreases in the depth of the optical sensor and forming a still further pn junction ( 25 , 29 ) together with the adjacent active region ( 20 ) and the p-substrate ( 52 ), a photo current thereof produced by light in the infrared wavelength range and tapped at a second cathode ( 28 );
an anode ( 40 ) is provided, connected to the p-substrate ( 52 ) via a terminal region ( 44 ), the p-substrate surrounding the active regions.
2. Sensor according to claim 1 , wherein the still further pn junction ( 25 , 29 ) also extends between the n-doped active region ( 24 ) and the p-substrate ( 52 ), in which this active region ( 24 ) is embedded, and wherein also at this pn junction ( 25 ) a photo current produced by light in the infrared wavelength range and being present or would be present at the second cathode ( 28 ).
3. Sensor according to claim 1 , wherein a layer ( 36 ; 60 ) is provided covering the first active region ( 12 ) at least in part, the layer being isolated with respect to the active regions ( 12 , 14 , 20 ) of the optical sensor.
4. Sensor according to claim 1 , wherein the first pn junction ( 22 ) is located at 0.2 μm to 0.5 μm measured from the top surface or the surface of the active portion of the sensor or is separated therefrom by said measure.
5. Sensor according to claim 1 , wherein a peak doping concentration of the doping profile of the third active region ( 20 ) is located at 3 μm to 5 μm and defines a boundary for the proportion of the visible photons.
6. Sensor according to claim 1 , wherein the first cathode ( 18 ) is at least a first cathode region or cathode portion that has a first contact ( 18 ).
7. Sensor according to claim 1 , wherein the second cathode ( 28 ) is at least a second cathode region or cathode portion that includes a second contact ( 28 ).
8. Sensor according to claim 1 , wherein the anode ( 40 ) is at least an anode region ( 40 , 44 ) having an anode contact ( 40 ) and a terminal region ( 44 ).
9. Sensor according to claim 1 , wherein the photo current at the first or second cathodes or the anode ( 18 , 28 , 40 ) or the anode ( 40 ) is present or produced at an electrically conductive contact of the respective anode or cathode.
10. Sensor according to claim 1 , wherein the infrared photo current can be tapped or is present at the second cathode ( 28 ) independent of a photo current generated from visible light in the pn junction ( 23 ) between the first active region ( 14 ) and the further active region ( 20 ).
11. Sensor according to claim 2 , wherein the still further pn junction ( 25 , 29 ) comprises two diode portions electrically connected in parallel, one towards the n-doped active region ( 24 ) and one towards the p-substrate ( 52 ).
12. Sensor according to claim 2 , wherein the p-doped active region ( 20 ) and the p-substrate ( 52 ) are at the same potential.
13. Sensor according to claim 3 , the layer being a polysilicon layer.