Avalanche photodiode device with a curved absorption region

A method for forming an APD device, wherein the method comprises:

• forming a first contact region and a second contact region in a semiconductor layer;
• forming an absorption region on the semiconductor layer, the absorption region comprises an intrinsic part and a doped part arranged side by side, wherein the absorption region is at least partly formed on a first region and the first contact region of the semiconductor layer, wherein the first region is arranged between the first contact region and the second contact region, wherein the intrinsic part is formed on the first region and the doped part is formed on the first contact region, wherein an upper surface of the absorption region is formed by the doped part, and wherein the absorption region is formed curved on the semiconductor layer;
• forming a charge region in the semiconductor layer between the first region and the second contact region;
• and
• forming an amplification region in the semiconductor layer between the charge region and the second contact region.