High performance, high electron mobility transistors with graphene hole extraction contacts
Radiation detectors based on high electron mobility transistors (HEMTs) are provided. Methods for detecting ultraviolet radiation using the HEMTs are also provided. The transistors are constructed from an intrinsic high bandgap semiconductor material with a built-in polarization field sandwiched between graphene and a two-dimensional electron gas (2DEG).
1. A vertical photodetector comprising:
a heterostructure comprising a first layer comprising a photoresponsive intrinsic semiconductor and a second layer comprising a second semiconductor;
a photogenerated electron extraction contact comprising a polarization charge-induced two-dimensional electron gas formed at an interface between the first layer and the second layer of the heterostructure;
a photogenerated hole extraction contact comprising a layer comprising electrically conducting graphene disposed over the first layer of the heterostructure in a vertical arrangement, such that the first layer of the heterostructure is disposed between the layer comprising the graphene and the two-dimensional electron gas;
an anode in contact with the graphene; and
a cathode in contact with the two-dimensional electron gas.
2. The photodetector of claim 1 , wherein the first intrinsic semiconductor is a first intrinsic Group III-V semiconductor and the second semiconductor is a second Group III-V semiconductor.
3. The photodetector of claim 1 , wherein the first intrinsic Group III-V semiconductor is AlGaN and the second Group III-V semiconductor is GaN.
4. The photodetector of claim 1 , wherein the first layer has a thickness of no greater than 100 nm.
5. The photodetector of claim 1 , wherein the first layer has a thickness of no greater than 50 nm.
6. The photodetector of claim 1 , wherein the heterostructure further includes a semiconductor cap layer over the first layer and the layer comprising electrically conducting graphene is disposed on the cap layer.
7. A vertical photodetector comprising:
a heterostructure comprising a first layer comprising a photoresponsive intrinsic semiconductor, a second layer comprising a second semiconductor, and a semiconductor interlayer between the first layer and the second layer;
a photogenerated electron extraction contact comprising a polarization charge-induced two-dimensional electron gas formed at an interface between the first layer and the second layer of the heterostructure;
a photogenerated hole extraction contact comprising a layer comprising electrically conducting graphene disposed over the first layer of the heterostructure in a vertical arrangement, such that the first layer of the heterostructure is disposed between the layer comprising the graphene and the two-dimensional electron gas;
an anode in contact with the graphene; and
a cathode in contact with the two-dimensional electron gas.
8. The photodetector of claim 7 , wherein the first intrinsic Group III-V semiconductor is AlGaN, the second Group III-V semiconductor is GaN, and the interlayer is an AN interlayer.
9. A method of detecting ultraviolet radiation using a vertical photodetector comprising:
a heterostructure comprising a first layer comprising a photoresponsive intrinsic semiconductor and a second layer comprising a second semiconductor;
a photogenerated electron extraction contact comprising a polarization charge-induced two-dimensional electron gas formed at an interface between the first layer and the second layer of the heterostructure;
a photogenerated hole extraction contact comprising a layer comprising electrically conducting graphene disposed over the first layer of the heterostructure in a vertical arrangement, such that the first layer of the heterostructure is disposed between the layer comprising the graphene and the two-dimensional electron gas;
an anode in contact with the graphene; and
a cathode in contact with the two-dimensional electron gas, the method comprising:
exposing the layer comprising electrically conducting graphene to incident ultraviolet radiation, wherein at least a portion of the incident ultraviolet radiation passes through the electrically conducting graphene and into the intrinsic semiconductor, generating electron-hole pairs;
extracting holes of the electron-hole pairs with the electrically conducting graphene; and
extracting electrons of the electron-hole pairs with the two-dimensional electron gas.
10. The method of claim 9 , wherein the first intrinsic semiconductor is AlGaN and the second semiconductor is GaN.
11. The method of claim 10 , wherein the photodetector has a signal-to-noise ratio of 10 5 or greater.
12. The method of claim 10 , wherein the photodetector has a response time of 2 ns or less.
13. The method of claim 10 , wherein the photodetector has a dark current of 1 pA or lower.