VERTICAL CAVITY SURFACE EMITTING LASER (VCSEL), LASER SENSOR AND METHOD OF PRODUCING A VCSEL
A vertical cavity surface emitting laser includes an optical resonator, a photodiode, and an electrical contact arrangement. The optical resonator includes a semiconductor multilayer stack. The semiconductor multilayer stack includes, in a direction of growth of the multilayer stack, a first distributed Bragg reflector, a second distributed Bragg reflector, and an active region for laser emission arranged between the first distributed Bragg reflector and second distributed Bragg reflector. The electrical contact arrangement is arranged to electrically pump the optical resonator and to electrically contact the photodiode. A reflectivity of the second distributed Bragg reflectoris higher than a reflectivity of the first distributed Bragg reflector. The photodiode has an absorbing region arranged in the second distributed Bragg reflector. A tunnel junction is arranged between the photodiode and the active region.
1 . A vertical cavity surface emitting laser, comprising:
an optical resonator,
a photodiode, and
an electrical contact arrangement,
wherein the optical resonator comprises a semiconductor multilayer stack, the semiconductor multilayer stack comprising, in a direction of growth of the multilayer stack, a first distributed Bragg reflector, a second distributed Bragg reflector, and an active region for laser emission arranged between the first distributed Bragg reflector and second distributed Bragg reflector,
wherein the electrical contact arrangement is arranged to electrically pump the optical resonator and to electrically contact the photodiode,
wherein a reflectivity of the second distributed Bragg reflectoris higher than a reflectivity of the first distributed Bragg reflector,
wherein the photodiode has an absorbing region arranged in the second distributed Bragg reflector, and
wherein a tunnel junction is arranged between the photodiode and the active region.
2 . The vertical cavity surface emitting laser of claim 1 , wherein the second distributed Bragg reflector has an outer first part and an inner or intermediate second part, wherein the absorbing region of the photodiode is arranged between the first part and the second part, wherein the outer first part is a p-doped region of the semiconductor multilayer stack, and the inner or intermediate second part is an n-doped region of the semiconductor multilayer stack.
3 . The vertical cavity surface emitting laser of claim 2 , wherein the second distributed Bragg reflector has an inner third part which is a p-doped region, wherein the tunnel junction is arranged between the second part and the third part of the second distributed Bragg reflector.
4 . The vertical cavity surface emitting laser of claim 1 , wherein a diameter or a width of the absorbing region is smaller than a diameter or a width of the active region.
5 . The vertical cavity surface emitting laser of claim 1 , wherein the absorbing region has a diameter or a width of less than 15 μm.
6 . The vertical cavity surface emitting laser of claim 1 , wherein the electrical contact arrangement is arranged to operate the photodiode and the tunnel junction with reverse bias and the active region with forward bias.
7 . The vertical cavity surface emitting laser of claim 1 , wherein the tunnel junction is arranged in or next to a node of a standing wave pattern of the laser emission in the optical resonator.
8 . The vertical cavity surface emitting laser of claim 1 , wherein the tunnel junction has a high or ultra-high doped n −− -layer.
9 . The vertical cavity surface emitting laser of claim 8 , wherein a dopant concentration in the n −− -layer is equal to or higher than 8×10 18 /cm 3 .
10 . The vertical cavity surface emitting laser of claim 1 , wherein the tunnel junction has a high or ultra-high doped p ++ -layer.
11 . The vertical cavity surface emitting laser of claim 10 , wherein a dopant concentration in the p ++ -layer is equal to or higher than 10 19 /cm 3 .
12 . The vertical cavity surface emitting laser of claim 1 , wherein the optical resonator comprises an oxide aperture or an ion implantation next to or in a vicinity of the absorbing region of the photodiode.
13 . The vertical cavity surface emitting laser of claim 1 , further comprising a substrate, wherein the substrate has an optical structure arranged on a surface of the substrate opposite to the multilayer stack.
14 . A laser sensor, comprising a vertical cavity surface emitting laser of claim 1 , wherein the laser sensor is at least one of a displacement sensor, a velocity sensor, a proximity sensor, a distance sensor, a particle sensor, or a contactless user interface sensor.
15 . A method of producing a vertical cavity surface emitting laser having an optical resonator and a photodiode, the method comprising:
growing a semiconductor multilayer stack, the semiconductor multilayer stack comprising a first distributed Bragg reflector, an active region for laser emission, and a second distributed Bragg reflector, the active region arranged between the first distributed Bragg reflector and the second distributed Bragg reflector, wherein the first distributed Bragg reflector, the active region, and the second distributed Bragg reflector form the optical resonator, wherein a reflectivity of the second distributed Bragg reflector is higher than a reflectivity of the first distributed Bragg reflector,
arranging an absorbing region of the photodiode in the second distributed Bragg reflector,
arranging a tunnel junction between the photodiode and the active region,
electrically contacting the optical resonator for pumping the active region, and
electrically contacting the photodiode.