Planar InGaAs Avalanche Photodiode With Multi-Stage InAlAs/InAlGaAs Multiplication Structure

A planar In0.53Ga0.47As avalanche photodiode (APD) with a triple-stage cascaded InAlAs/InAlGaAs multiplication structure is designed and fabricated. Double zinc-diffusion p-n junction is formed to suppress the perimeter premature breakdown. A low dark current of 4.8 nA at around breakdown voltage is obtained at room temperature for a 40 mu m diameter device with a maximum gain-bandwidth product of 216 GHz. The E-field profile is modulated by doping of a thin In0.52Al0.48As subcharge layer within each multiplication stage. Moreover, electron and hole potential wells are also introduced by the In0.52Al0.24Ga0.24As layers within each stage. The measured hole-initiated maximum gain factor and excess noise factor are 77 and F=6.3 at 200 K, respectively, which well agree with the predicted results base on the dead-space multiplication theory. These results indicate the planar multi-stage multiplication regime is a viable route for fabrication of APDs towards low excess noise while maintaining of a low dark current.