Suppression of avalanche multiplication at the periphery of diffused junction by floating guard rings in a planar InGaAs-InP avalanche photodiode

We obtained a series of experimental results showing the effects of floatin g guard rings (FGR's) in InGaAs-InGaAsP-InP separate absorption, grading, c harge, and multiplication avalanche photodiodes, It was confirmed from the scanned photocurrent curves that the essential role of FGR's is to disperse the curved equipotential lines at the lateral junction periphery and to gi ve a low field route for a carrier beneath the FGR's. FGR effect mainly dep ends on guard ring spacing and it also depends on the magnitude of the appl ied bias, In our optimum guard ring condition, the current gain at the acti ve planar region found to be 1.4 times larger than that at the curved edge.