Signal amplification and leakage current suppression in amorphous silicon P-I-N diodes by field profile tailoring

The performance of amorphous silicon p-i-n diodes as radiation detectors in terms of signal amplitude can be greatly improved when there is a built-in signal gain mechanism. We describe an avalanche gain mechanism which is achieved by introducing stacked intrinsic, p-type, and n-type layers into the diode structure. We replaced the intrinsic layer of the conventional p-i-n diode with i(1)-p-i(2)-n-i(3) multilayers. The i(2) layer (typically 1 similar to 3 mu m) achieves an electric field > 10(6) V/cm, while maintaining the p-i interfaces to the metallic contact at electric fields < 7 x 10(4) V/cm, when the diode is fully depleted. For use in photo-diode applications the whole structure is less than 10 mu m thick. Avalanche gains of 10 similar to 50 can be obtained when the diode is biased to similar to 500 V. Also, dividing the electrodes to strips of 2 mu m width and 20 mu m pitch reduced the leakage current up to an order of magnitude, and increased light transmission without creating inactive regions.