Germanium-based sensor with junction-gate field effect transistor and method of fabricating thereof

A method for forming a photosensitive device, the method comprising:

• forming a first dielectric layer over a substrate of a first semiconductor material;
• etching the first dielectric layer to form a trench in the first dielectric layer, wherein the trench has sidewalls formed by the first dielectric layer and a bottom formed by the substrate;
• forming a first semiconductor layer of the first semiconductor material that partially fills and lines the bottom and the sidewalls of the trench;
• forming a second semiconductor layer of a second semiconductor material that fills a remainder of the trench and is over the first semiconductor layer;
• after forming a second dielectric layer over the second semiconductor layer, forming a first doped region, a second doped region, a third doped region, a fourth doped region, a fifth doped region, and a sixth doped region in the second semiconductor layer, wherein:
• the first doped region is between the second doped region and the third doped region, the fifth doped region overlaps the first doped region and the second doped region, the sixth doped region overlaps the first doped region and the third doped region, and the fourth doped region is between the fifth doped region and the sixth doped region,
• the first doped region, the fifth doped region, and the sixth doped region include a first type dopant, and
• the second doped region, the third doped region, and the fourth doped region include a second type dopant;
• and
• forming a third semiconductor layer of a third semiconductor material and a fourth semiconductor layer of the third semiconductor material over the fourth doped region, wherein the third semiconductor layer and the fourth semiconductor layer include the second type dopant, the third semiconductor layer and the fourth semiconductor layer are between the fifth doped region and the sixth doped region, and the third semiconductor layer and the fourth semiconductor layer are disposed in the second dielectric layer.

A photosensitive device comprising:

• a substrate of a first semiconductor material;
• a first semiconductor layer of the first semiconductor material and a second semiconductor layer of a second semiconductor material, wherein the first semiconductor layer is disposed between the second semiconductor layer and the substrate;
• a first doped region, a second doped region, and a third doped region disposed in the second semiconductor layer, wherein the first doped region is disposed between the second doped region and the third doped region, the first doped region includes a first type dopant, and the second doped region and the third doped region include a second type dopant;
• a fourth doped region, a fifth doped region, and a sixth doped region disposed in the second semiconductor layer, wherein the fourth doped region is disposed between the fifth doped region and the sixth doped region, the fourth doped region is disposed over the first doped region, the fifth doped region overlaps the first doped region and the second doped region, the sixth doped region overlaps the first doped region and the third doped region, the fourth doped region includes the second type dopant, and the fifth doped region and the sixth doped region include the first type dopant;
• a dielectric layer disposed over the first semiconductor layer and the second semiconductor layer;
• and
• a third semiconductor layer and a fourth semiconductor layer disposed in the dielectric layer, disposed over the fourth doped region, and disposed between the fifth doped region and the sixth doped region, wherein the third semiconductor layer and the fourth semiconductor layer are of a third semiconductor material and include the second type dopant.