Abstract
While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. In this paper we report a graphene/GaSe nanosheets hybrid photodetector, in which GaSe nanosheets provide a favorable geometric link to graphene conductive layer through van Der Waals force. After a vacuum annealing process, a high gain in exceeding 107 has been obtained simitaneously with a dynamic response time of around 10 ms for both light on and off. We attribute the high performance to the elimination of possible deep charge traps, most probably at the graphene/GaSe nanosheets interface. This result demonstrates high photoconductive gain and fast photoresponse can be achieved simultaneously and a clean interface is the key to the high performance of these hybrid devices.
Highlights
While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications
An ultrahigh photoconductive gain of 108 charge carriers per photon and a high responsivity up to 107 A/W were obtained in a hybrid graphene/semiconductor quantum dot (QD)16, graphene/two-dimensional transition/post-transition metal dichalcogenides (TMDC), such as MoS2 and WSe217–19, field-effect devices (FETs)
Gallium selenide (GaSe) nanosheets were synthesized from bulk GaSe and details are summarized in Methods35
Summary
While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. An ultrahigh photoconductive gain of 108 charge carriers per photon and a high responsivity up to 107 A/W were obtained in a hybrid graphene/semiconductor quantum dot (QD), graphene/two-dimensional transition/post-transition metal dichalcogenides (TMDC), such as MoS2 and WSe217–19, field-effect devices (FETs). In these devices, one type of the photoexcited carriers in the PbS-QD (or TMDC nanosheets) absorption layer is transferred into the graphene layer and circulate many times due to the high mobility of graphene within the lifetime of the oppositely charged carriers in the PbS-QDs, resulting in a photoconductive gain.
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