Long wavelength vertical cavity surface emitting laser with monolithically grown photodetector
A long wavelength vertical cavity surface emitting laser (VCSEL) with a monolithically-grown photodetector is provided. The photodetector is installed in a middle portion of or on a bottom surface of a lower distributed Bragg reflector of the long wavelength VCSEL. The photodetector is integrated with the long wavelength VCSEL. A substrate on which the long wavelength VCSEL and the photodetector are crystal-grown does not absorb a laser beam emitted from the long wavelength VCSEL. Thus, the laser beam heading toward the substrate is accurately detected, and the gain of the laser beam is effectively controlled.
1. A long wavelength vertical cavity surface emitting laser configuration comprising:
a semiconductor substrate;
a photodetector located on said semiconductor;
a lower distributed Bragg reflector, which includes multiple layers and is grown on the photodetector;
an active region, which includes multiple semiconductor material layers which emit long wavelength light upon excitation and is grown on the lower distributed Bragg reflector; and
an upper distributed Bragg reflector, which includes multiple layers and is grown on the active region,
wherein the photodetector detects a laser beam emitted from the active region that heads toward semiconductor substrate,
wherein both shoulders of the photodetector are exposed so that a stack including the lower distributed Bragg reflector, the active region, and the upper distributed Bragg reflector has a column shape on the photodetector, and
wherein the photodetector comprises a PIN photodiode having a p-doped layer, an n-doped layer and an absorbing layer, and further comprising at least one upper photodiode formed on the upper distributed Bragg reflector, at least an intermediate electrode formed on the PIN electrode, and a lower electrode formed on a bottom surface of the semiconductor substrate, said lower electrode being shared by the active region and the PIN photodiode.
2. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the substrate is made of gallium arsenide (GaAs).
3. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the substrate is made of indium phosphide (InP).
4. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the substrate is made of one of GaAs and InP.
5. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the substrate is made of GaAs, and the active region is made of an InGaAs quantum well layer.
6. The long wavelength vertical cavity surface emitting laser of claim 1 , wherein the substrate is made of GaAs, and the active region is made of one of an indium gallium arsenide nitride (InGaAsN) quantum well layer, and an In(Ga)(N)As quantum dot layer.
7. The long wavelength vertical cavity surface emitting laser of claim 1 , wherein the substrate is made of GaAs, and an absorbing layer of the photo detector includes one of an InGaAs quantum well, an indium gallium arsenide nitride (InGaAsN) quantum well, and an In(Ga)(N)As quantum dot.
8. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein each of the upper and lower distributed Bragg reflectors is an (Al)GaAs/Al(Ga)As stack.
9. The long wavelength vertical cavity surface emitting laser configuration of claim 4 , wherein each of the upper and lower distributed Bragg reflectors is an (Al)GaAs/Al(Ga)As stack.
10. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the substrate is made of InP, and the active region is made of an InGaAsP quantum well layer.
11. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the substrate is made of InP, and the active region is made of one of an InGaAlAs quantum well layer, an InGaAs quantum well layer, an In(Ga)(N)As quantum dot layer, and an aluminum gallium arsenide stibium (AlGaAsSb) quantum well layer.
12. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the substrate is made of InP, and an absorbing layer of the photo detector includes one of an InGaAsP quantum well, an InGaAlAs quantum well, an InGaAs quantum well, an In(Ga)(N)As quantum dot, and an AlGaAsSb quantum well.
13. The long wavelength vertical cavity surface emitting laser configuration of claim 10 , wherein each of the upper and lower distributed Bragg reflectors is an InP/InGaAsP or InP/InGaAlAs stack.
14. The long wavelength vertical cavity surface emitting laser configuration of claim 11 , wherein each of the upper and lower distributed Bragg reflectors is an InP/InGaAsP or InP/InGaAlAs stack.
15. The long wavelength vertical cavity surface emitting laser configuration of claim 1 , wherein the absorbing layer has a band gap that is less than or the same as that of the active layer.