Method of forming an electrical metal contact and method of producing a vertical cavity surface emitting laser
A method of forming an electrical metal contact within a semiconductor layer stack of a vertical cavity surface emitting laser includes forming a contact hole into the semiconductor layer stack. The contact hole has a bottom and a side wall extending from the bottom. The method further includes providing a photoresist mask inside the contact hole. The photoresist mask covers the side wall of the contact hole and has an opening extending to the bottom of the contact hole. The method additionally includes wet-chemical isotropic etching the bottom of the contact hole, depositing a metal on the bottom of the contact hole, and removing the photoresist mask so that the metal on the bottom of the contact hole is left as the electrical metal contact.
1. A method of forming an electrical metal contact within a semiconductor layer stack of a vertical cavity surface emitting laser, the method comprising:
forming a contact hole into the semiconductor layer stack, the contact hole having a bottom and a side wall extending from the bottom, wherein the contact hole is formed with a depth of more than 10 μm,
providing a photoresist mask inside the contact hole, the photoresist mask covering the side wall of the contact hole, the photoresist mask having an opening extending to the bottom of the contact hole,
wet-chemical isotropic etching the bottom of the contact hole,
depositing a metal on the bottom of the contact hole, and
removing the photoresist mask so that the metal on the bottom of the contact hole is left as the electrical metal contact.
2. The method of claim 1 , wherein the photoresist mask comprises a positive-tone photoresist.
3. The method of claim 1 , further comprising, prior to depositing the metal on the bottom of the contact hole, removing oxide from the bottom of the contact hole.
4. The method of claim 3 , wherein removing oxide from the bottom of the contact hole comprises Ar-sputtering.
5. The method of claim 1 , wherein providing the photoresist mask in the contact hole comprises lithographically structuring the photoresist mask to provide the opening through the photoresist mask to the bottom of the contact hole.
6. The method of claim 1 , further comprising, after removing the photoresist mask, applying an electrical passivation layer on the side wall of the contact hole.
7. The method of claim 1 , wherein removing the photoresist mask comprises a chemically induced lifting off of the photoresist mask.
8. The method of claim 1 , wherein the semiconductor layer stack comprises a distributed Bragg reflector, and the contact hole is formed into the distributed Bragg reflector.
9. The method of claim 1 , wherein the semiconductor layer stack is arranged on a substrate, and wherein the contact hole is formed into the semiconductor layer stack down to a semiconductor layer of the layer stack above the substrate.
10. The method of claim 1 , wherein the semiconductor layer stack is arranged on a substrate, and wherein the contact hole is formed into the semiconductor layer stack down to the substrate.
11. The method of claim 1 , wherein the contact hole is formed using etching, in particular non-selective etching.
12. A method of producing a vertical cavity surface emitting laser, the method comprising:
providing a semiconductor layer stack, and
forming an electrical metal contact within the semiconductor layer stack using the method according to claim 1 .