FAST, HIGH-DENSITY AVALANCHE PHOTODIODE-ARRAY

Using bevelled edge avalanche photodiode technology, we have built a high density 64-element array, with center-to-center spacing of 450 mum. The array was built by etching grooves in the back side of a large area avalanche photodiode. The pattern for etching and metalization of the pixels on the back side was done with photolithography. This technique allows for good control of the groove depth. The cross talk between pixels is related to the resistance between them and is dependent on the bias applied to the detector. Because of the small pixel size, the rise time with an impulse excitation approaches approximately 0.9 ns. These arrays have very good potential for light or low energy x-ray imaging systems and optical fiber readout in detectors for high energy physics detectors.