Germanium photodetector

1. A method for forming a photodetector device, the method including:

forming an insulator layer on a substrate;

forming a germanium (Ge) layer on the insulator layer and a portion of the substrate;

forming a second insulator layer on the Ge layer;

implanting n-type ions in the Ge layer;

patterning the n-type Ge layer;

forming a capping insulator layer on the second insulator layer and a portion of the first insulator layer;

heating the device to crystallize the Ge layer resulting in an single crystalline n-type Ge layer; and

forming electrodes electrically connected to the single crystalline n-type Ge layer.

2. The method of claim 1 , wherein the method further includes forming a germanide material between the electrodes and the single crystalline n-type Ge layer.

3. The method of claim 2 , wherein the germanide material is formed by depositing a layer of metal on an exposed portion of the single crystalline n-type Ge layer and heating the device to diffuse the metal into the single crystalline n-type Ge layer.

4. The method of claim 3 , wherein the layer of metal includes titanium, and the device is heated at a temperature greater than 300° C.

5. A method for forming a photodetector device, the method including:

forming an insulator layer on a substrate;

forming a germanium (Ge) layer on the insulator layer and a portion of the substrate;

forming a second insulator layer on the Ge layer;

implanting n-type ions in the Ge layer;

patterning the n-type Ge layer to remove portions of the second insulator layer and the n-type Ge layer;

forming a capping insulator layer on the second insulator layer and a portion of the first insulator layer;

heating the device to crystallize the Ge layer resulting in an single crystalline n-type Ge layer; and

forming electrodes electrically connected to the single crystalline n-type Ge layer.