InGaAs/InP SAM Photodetectors Fabricated by Structure Controlled Acceptor Diffusion

The Cd-diffusion at InP/InGaAs heterojunctions was investigated by C-V profiling of p-n junctions located on the InP-side close to the heterointerface. A compensated layer in front of the heterojunction is observed. Reducing the distance p-n junction-heterointerface decreases the width of this layer causing a distinct drop of the breakdown voltage of the junction. This effect is used to realize SAM APD´s with guard ring by a structure controlled modulation of the distance p-n junction-hetero-interface. Avalanche gain up to M = 15 is achieved. The breakdown voltage in the multiplication area is at least 40% smaller than in the guard ring area. A background doping level ND= 2-3.10¹⁶cm^¿3 in the InP-layer is required for optimum detector operation.