VERTICAL CAVITY SURFACE EMITTING LASER AND METHOD OF PRODUCING SAME
A method of producing a Vertical Cavity Surface Emitting Laser, including providing a layer stack of semiconductor layers including a first mirror, a second mirror, an active region between the first and second mirrors, an Al 1-x Ga x As layer with 0≤x≤0.05, and a contact layer immediately adjacent to the Al 1-x Ga x As layer. The method further includes etching the layer stack to obtain a first layer sub-stack forming a mesa and a second layer sub-stack adjacent to the mesa in a stacking direction of the layer stack. Layers of the second layer sub-stack extend beyond layers of the first layer sub-stack in a direction perpendicular to the stacking direction. The Al 1-x Ga x As layer is used as an etch-stop layer. The method further includes removing an outer part of the Al 1-x Ga x As layer to expose, at least partly, the contact layer, and oxidizing the Al 1-x Ga x As layer to obtain an oxide aperture layer.
1 : A method of producing a Vertical Cavity Surface Emitting Laser, the method comprising:
providing a layer stack of semiconductor layers, the semiconductor layers of the layer stack including a first mirror, a second mirror, an active region between the first and second mirrors, an Al 1-x Ga x As layer with 0≤x≤0.05, and a contact layer immediately adjacent to the Al 1-x Ga x As layer;
etching the layer stack to obtain a first layer sub-stack forming a mesa and a second layer sub-stack adjacent to the mesa in a stacking direction of the layer stack, wherein layers of the second layer sub-stack extend beyond layers of the first layer sub-stack in a direction perpendicular to the stacking direction, and wherein the Al 1-x Ga x As layer is used as an etch-stop layer;
removing an outer part of the Al 1-x Ga x As layer to expose, at least in part, the contact layer; and
oxidizing the Al 1-x Ga x As layer to obtain an oxide aperture layer.
2 : The method of claim 1 , wherein the etching includes a selective etching process which automatically stops at the Al 1-x Ga x As layer.
3 : The method of claim 2 , wherein the selective etching process is a selective wet-chemical or a dry chemical etching process.
4 : The method of claim 2 , wherein the selective etching process is preceded by an initial etching process, the method further comprising stopping the initial etching process one or more layers apart from the Al 1-x Ga x As layer.
5 : The method of claim 4 , wherein the initial etching process is a dry etching process.
6 : The method of claim 1 , wherein the oxide aperture layer forms a current aperture.
7 : The method of claim 1 , wherein the oxide aperture layer is a last layer of the mesa.
8 : The method of claim 1 , wherein the layer stack of semiconductor layers form an optical resonator.
9 : The method of claim 8 , wherein the contact layer is arranged in a node of a standing wave field of laser light in the optical resonator.
10 : The method of claim 1 , wherein the contact layer has a doping concentration sufficient for ohmic behavior of the contact layer.
11 : The method of claim 10 , wherein the doping concentration in the contact layer gradually decreases in a thickness direction of the contact layer from a side facing the oxide aperture layer to an opposite side, or
wherein the doping concentration gradually decreases from the contact layer to an adjacent layer on a side of the contact layer facing away from the oxide aperture layer.
12 : The method of claim 1 , wherein the contact layer has a thickness of at least 10 nm.
13 : The method of claim 1 , wherein the contact layer is a p-doped contact layer.
14 : The method of claim 1 , further comprising providing a photodiode having an intrinsic absorption region and integrating the intrinsic absorption region into the first mirror and/or the second mirror.
15 : The method of claim 14 , wherein the second mirror has a first portion facing the contact layer, which is a p-doped region of the layer stack, and a second portion facing away from the contact layer, which is an n-doped region of the layer stack, and wherein the intrinsic absorption region of the photodiode is arranged between the first and second portions of the second mirror.
16 : The method of claim 1 , wherein the first mirror is an n-doped region of the layer stack.
17 : The method of claim 1 , wherein at least one mirror layer pair of the second mirror is arranged between the active region and the oxide aperture layer.