Image sensor with passivation layer for dark current reduction

An image sensor comprising:

• a substrate;
• a device layer overlying the substrate;
• a cap layer overlying the device layer, wherein the cap and device layers and the substrate are semiconductor materials, and wherein the device layer is a different semiconductor material than the substrate and the cap layer;
• a photodetector in the device and cap layers;
• a first dielectric layer overlying and directly contacting the cap layer;
• and
• a second dielectric layer overlying and directly contacting the first dielectric layer, wherein the first and second dielectric layers comprise oxide, and wherein the second dielectric layer has a higher dielectric constant than the first dielectric layer.

A method for forming an image sensor comprising:

• epitaxially growing a device layer overlying a substrate;
• epitaxially growing a cap layer overlying the device layer, wherein the cap layer has a larger bandgap than the device layer;
• forming a photodetector in the device and cap layers;
• and
• depositing a passivation layer overlying the cap layer, wherein the passivation layer induces formation of a dipole moment along a top surface of the cap layer.