Photo-field-effect transistor devices and associated methods are disclosed in which a photogate, consisting of a quantum dot sensitizing layer, transfers photoelectrons to a semiconductor channel across a charge-separating (type-II) heterointerface, producing a sustained primary and secondary flow o
Photo-field-effect transistor devices and associated methods are disclosed in which a photogate, consisting of a quantum dot sensitizing layer, transfers photoelectrons to a semiconductor channel across a charge-separating (type-II) heterointerface, producing a sustained primary and secondary flow of carriers between source and drain electrodes. The light-absorbing photogate thus modulates the flow of current along the channel, forming a photo-field effect transistor.
대표청구항▼
1. A photo-field effect transistor device comprising: an electrically insulating substrate;source and drain electrodes provided on said substrate in a spaced relationship;a carrier-accepting semiconductor channel contacting said substrate between said source and drain electrodes, wherein said carrie
1. A photo-field effect transistor device comprising: an electrically insulating substrate;source and drain electrodes provided on said substrate in a spaced relationship;a carrier-accepting semiconductor channel contacting said substrate between said source and drain electrodes, wherein said carrier-accepting semiconductor channel is in electrical communication with said source and drain electrodes; anda light absorbing quantum dot sensitizing layer contacting said carrier-accepting semiconductor channel, said quantum dot sensitizing layer producing photo-generated carriers under illumination of light within a selected optical bandwidth;wherein an interface between said quantum dot sensitizing layer and said carrier-accepting semiconductor channel forms a type II heterojunction configured to inject one type of said photo-generated carriers into said carrier-accepting semiconductor channel, thereby producing primary photocarriers within said carrier-accepting semiconductor channel; andwherein said carrier-accepting semiconductor channel is characterized by a mobility such that under application of a voltage difference between said source and drain electrodes and under illumination of said quantum dot sensitizing layer, a photocurrent is produced due to injection of the primary photocarriers and recirculation of secondary photocarriers. 2. The photo-field effect transistor device according to claim 1 wherein a bandgap of said quantum dot sensitizing layer is smaller than a bandgap of said carrier-accepting semiconductor channel. 3. The photo-field effect transistor device according to claim 2 wherein quantum dot sensitizing layer has a bandgap configured to cause absorption of light over the selected optical bandwidth, and wherein said carrier-accepting semiconductor channel has a bandgap configured to be substantially transparent to light over said selected optical bandwidth, such that photogenerated carriers within said carrier-accepting semiconductor channel are provided predominantly through injection from said quantum dot sensitizing layer. 4. The photo-field effect transistor device according to claim 1 wherein said quantum dot sensitizing layer has thickness selected such that when the device is illuminated with light within the selected optical bandwidth from a side associated with said quantum dot sensitizing layer, a substantial fraction of incident optical power is absorbed within the quantum dot sensitizing layer. 5. The photo-field effect transistor device according to claim 1 wherein said interface between said quantum dot sensitizing layer and said carrier-accepting semiconductor channel is a type II heterojunction configured to inject electrons into said carrier-accepting semiconductor channel. 6. The photo-field effect transistor device according to claim 5 wherein said carrier-accepting semiconductor channel comprises an aluminum doped zinc oxide layer, and wherein the primary photocarriers are electrons. 7. The photo-field effect transistor device according to claim 6 wherein an oxygen content of said aluminum doped zinc oxide layer is selected to provide a suitable electron affinity for injection of the electrons. 8. The photo-field effect transistor device according to claim 7 wherein an oxygen content of said aluminum doped zinc oxide layer is between approximately 5 percent and 20 percent. 9. The photo-field effect transistor device according to claim 1 wherein said quantum dot sensitizing layer is a sub-monolayer of quantum dots. 10. The photo-field effect transistor device according to claim 1 wherein said quantum dot sensitizing layer comprises quantum dots selected from the group consisting of PbS nanoparticles, PbSe nanoparticles, CdS nanoparticles, CdSe nanoparticles, ZnS nanoparticles, and PbS nanoparticles. 11. The photo-field effect transistor device according to claim 1 wherein said carrier-accepting semiconductor channel comprises a semiconductor material selected from the group consisting of graphene, carbon nanotubes, TiO2, ZrO, and ZnO. 12. The photo-field effect transistor device according to claim 1 wherein one or both of said source and drain electrodes comprises a conductive material selected from the group consisting of TiN, TaN, Al, W, Au, Pt, Pd, polySi, and PtSi. 13. The photo-field effect transistor device according to claim 1 wherein a thickness of said carrier-accepting semiconductor channel is less than 50 nm. 14. The photo-field effect transistor device according to claim 1 wherein a mobility of said carrier-accepting semiconductor channel is greater than or equal to approximately 104 cm2/Vs. 15. The photo-field effect transistor device according to claim 1 wherein a diffusion length of said primary photocarriers is approximately greater than or equal to a thickness of said quantum dot sensitizing layer. 16. The photo-field effect transistor device according to claim 1 wherein minority carrier diffusion determines transport of said primary photocarriers from said quantum dot sensitizing layer to said carrier-accepting semiconductor channel, and wherein a minority carrier diffusion length of said primary photocarriers exceeds approximately 0.1 cm2/Vs. 17. The photo-field effect transistor device according to claim 1 wherein a mobility, free carrier density, and thickness of said carrier-accepting semiconductor channel are selected to provide a dark current less than or equal to approximately 0.1 fA per 1 um2 of surface area. 18. A method of generating photoconductive gain in a photo-field effect transistor device according to claim 1, the method comprising: illuminating said photo-field effect transistor device with light within said selected optical bandwidth, wherein said photo-field effect transistor device is illuminated from a side associated with said quantum dot sensitizing layer;applying a voltage difference between said source and drain electrodes; anddetecting a resulting photocurrent. 19. The method according to claim 18 wherein quantum dot sensitizing layer has a bandgap configured to cause absorption of light over the selected optical bandwidth, and wherein the carrier-accepting semiconductor channel has a bandgap configured to be substantially transparent to light over the selected optical bandwidth, such that photogenerated carriers within the carrier-accepting semiconductor channel are provided predominantly through injection from the quantum dot sensitizing layer. 20. The method according to claim 18 wherein the quantum dot sensitizing layer has thickness selected such that when the device is illuminated with light within the selected optical bandwidth, a substantial fraction of the incident optical power is absorbed within the quantum dot sensitizing layer.
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