Germanium-on-silicon avalanche photodetector in silicon photonics platform, method of making the same

An avalanche photodetector comprising:

• a silicon layer having a junction embedded in the silicon layer, the junction being a p-type-intrinsic-n-type (PIN) junction and formed of:
• a first embedded layer embedded disposed beneath an external surface of the silicon layer, the first embedded layer being doped in a n+ doping state,
• a second embedded layer disposed above the first embedded layer, the second embedded layer being (i) in contact with the external surface of the silicon layer, and (ii) doped in a p doping state, and
• a third embedded layer disposed between the first embedded layer and the second embedded layer, the third embedded layer being in an intrinsic state,
• an epitaxial germanium layer formed over the junction, the epitaxial germanium layer being in either an intrinsic state or a p doping state and being configured to function as a light absorption layer to absorb light;
• and
• a plurality of electrode regions formed in the silicon layer and in the epitaxial germanium layer, the electrode regions being configured to apply a reverse bias voltage across the junction to induce a photoelectric effect to convert light energy to electrical energy.

A method of fabricating an avalanche photodetector, the method comprising:

• forming a silicon-on-insulator substrate comprising:
• forming an oxide layer of the silicon-on-insulator substrate, and
• depositing a silicon layer on the oxide layer, wherein a central region of the silicon layer comprises a n+ doped layer embedded in the silicon layer,
• forming an embedded junction within the silicon substrate by performing (i) a first ion-implementation process to implant a p-type impurity into the silicon layer to neutralize a top portion of the embedded n+ doped layer from its n+ doping state to an intrinsic state to form in the central region an embedded intrinsic layer overlaying an embedded n+ doping layer, and (ii) a second ion-implementation process to further p-type impurity dope a top portion of the central region to form a p doped layer embedded in the silicon layer above the n+ doped layer;
• depositing on the central region an epitaxial germanium layer, which is in an intrinsic state or a p doping state and configured to function as a light absorption layer to absorb light;
• and
• forming, in the silicon layer and in the epitaxial germanium layer, a plurality of electrode regions that are configured to apply a reverse bias voltage across the embedded junction to cause a photoelectric effect to convert light energy to electrical energy.

An avalanche photodetector comprising:

• a silicon layer having a junction embedded in the silicon layer and being a p-type-n-type (PN) junction, the junction formed of
• a first embedded layer embedded beneath an external surface of the silicon layer and doped in a n+ doping state, and
• a second embedded layer disposed above the first embedded layer and in contact with the external surface of the silicon layer, the second embedded layer doped in a p doping state,
• an epitaxial germanium layer formed over the junction, the epitaxial germanium layer being in an intrinsic state or a p doping state and configured to function as a light absorption layer to absorb light;
• and
• a plurality of electrode regions formed in the silicon layer and in the epitaxial germanium layer and configured to apply a reverse bias voltage across the junction to induce a photoelectric effect to convert light energy to electrical energy.

A method of fabricating an avalanche photodetector, the method comprising:

• forming a silicon-on-insulator substrate comprising:
• forming an oxide layer of the silicon-on-insulator substrate, and
• depositing a silicon layer on the oxide layer, wherein a central region of the silicon layer comprises a n+ doped layer embedded in the silicon layer,
• forming an embedded junction within the silicon substrate by performing at least one ion-implementation process to (i) implant a p-type impurity into the silicon layer to neutralize a top portion of the embedded n+ doped layer from its n+ doping state to an intrinsic state to form in the central region an embedded intrinsic region overlaying an embedded n+ doping layer, and (ii) p-type impurity dope embedded intrinsic region to form a p doped layer embedded in the silicon layer above the n+ doped layer;
• depositing on the central region an epitaxial germanium layer, which is in an intrinsic state or a p doping state and configured to function as a light absorption layer to absorb light;
• and
• forming, in the silicon layer and in the epitaxial germanium layer, a plurality of electrode regions that are configured to apply a reverse bias voltage across the embedded junction to cause a photoelectric effect to convert light energy to electrical energy.