SiGe or germanium flip chip optical receiver

An opto-electronic system comprising:

• a semiconductor substrate having a first surface and a second surface opposite said first surface, a first semiconductor layer of a first semiconductor material adjacent said first surface, said first semiconductor layer on a second semiconductor of a second semiconducting material, said first semiconducting material having a higher absorption coefficient than said second semiconducting material when both said first semiconducting material and said second semiconducting material are undoped;
• a device in said first semiconductor layer to collect carriers generated by an optical signal;
• and
• an optical transmitter shining said optical signal on said second surface wherein said optical signal has a wavelength, wherein a portion of said optical signal can pass through said second semiconductor layer but is absorbed by said first semiconductor material in said first semiconductor layer for collection by said device.

A method for providing a signal comprising the steps of:

• a) providing a first semiconducting material on a second semiconducting material;
• b) providing a device in said first material for receiving an optical signal;
• c) directing an optical signal to said second semiconducting material, said optical signal having a wavelength, wherein a portion of said optical signal passes through said second semiconducting material and is absorbed by said first semiconducting material, wherein said first semiconducting material has a higher absorption coefficient than said second semiconducting material when both said first semiconducting material and said second semiconducting material are undoped;
• and
• d) generating an electrical signal in said device based on said absorbed optical signal.