An improved tunnel junction structure and a VCSEL that uses this structure is disclosed. The tunnel junction includes first, second, and third layers that include materials of the InP family of materials. The first layer is doped with n-type dopant species to a concentration of 10.sup.19 dopant atoms per cm.sup.3 or greater. The second layer is doped with Zn to a similar concentration and is in contact with the first layer. The interface between the first and second layers forms a tunnel junction. The third layer includes a material that retards the diffusion of Zn out of the second layer. The third layer preferably includes undoped AlInAs. The tunnel junction structure of the present invention can be utilized in a VCSEL having an active layer between first and second mirrors that are both constructed from n-type semiconductor layers.