Tensile strained semiconductor photon emission and detection devices and integrated photonics system
Tensile strained germanium is provided that can be sufficiently strained to provide a nearly direct band gap material or a direct band gap material. Compressively stressed or tensile stressed stressor materials in contact with germanium regions induce uniaxial or biaxial tensile strain in the germanium regions. Stressor materials may include silicon nitride or silicon germanium. The resulting strained germanium structure can be used to emit or detect photons including, for example, generating photons within a resonant cavity to provide a laser.
1. A method of processing a semiconductor formation that includes a layer of germanium disposed over a semiconductor substrate, the method comprising:
forming a silicon nitride mask over the layer of germanium layer, and defining openings in the mask;
etching areas of the layer of germanium exposed by the openings in the mask to form corresponding recesses in the germanium layer;
filling the recesses with epitaxial silicon germanium.
2. The method of claim 1 , wherein filling the recesses is by one of selective chemical vapor deposition within the corresponding recesses in germanium layer defined by the openings in the mask, or non-selective chemical vapor deposition with subsequently planarizing the formation to remove deposited silicon germanium over the silicon nitride mask.
3. The method of either one of claim 2 , further comprising growing an oxide film over exposed surfaces of the silicon germanium.
4. The method of claim 3 , wherein the oxide film comprises one of silicon oxide or silicon germanium oxide.
5. The method of claim 4 , further comprising removing the silicon nitride using a selective wet etch.
6. The method of claim 5 , wherein the layer of germanium is an n-type epitaxial germanium layer.
7. The method of claim 5 , wherein prior to forming the silicon nitride mask, the layer of germanium is deposited epitaxially on the semiconductor substrate.
8. The method of claim 5 , wherein n-type doping of the layer of germanium is performed in situ during deposition of the layer of germanium.
9. The method of claim 5 , wherein the openings in the mask are defined by lithography and dry etching.
10. The method of claim 5 , wherein the openings in the mask define a pattern above the layer of germanium.
11. The method of claim 10 , wherein the pattern comprises a matrix pattern.
12. The method of claim 11 , wherein the matrix pattern is a checkerboard pattern.
13. The method of claim 5 , wherein said etching through layer of germanium continues into the semiconductor substrate.
14. The method of claim 2 , wherein the silicon germanium comprises one of undoped, doped p-type, or doped n-type silicon germanium.
15. The method of claim 14 , further comprising forming electrical contacts to the layer of germanium.