Light-modulated vertical heterojunction phototransistors with distinct logical photocurrents
Jiayue Han, Meiyu He, Ming Yang, Qi Han, Fang Wang, Fang Zhong, Mengjian Xu, Qing Li, He Zhu, Chongxin Shan, Weida Hu, Xiaoqing Chen, Xinran Wang, Jun Gou, Zhiming Wu, Jun Wang
Abstract
Abstract The intriguing carrier dynamics in graphene heterojunctions have stimulated great interest in modulating the optoelectronic features to realize high-performance photodetectors. However, for most phototransistors, the photoresponse characteristics are modulated with an electrical gate or a static field. In this paper, we demonstrate a graphene/C 60 /pentacene vertical phototransistor to tune both the photoresponse time and photocurrent based on light modulation. By exploiting the power-dependent multiple states of the photocurrent, remarkable logical photocurrent switching under infrared light modulation occurs in a thick C 60 layer (11 nm) device, which implies competition of the photogenerated carriers between graphene/C 60 and C 60 /pentacene. Meanwhile, we observe a complete positive-negative alternating process under continuous 405 nm irradiation. Furthermore, infrared light modulation of a thin C 60 (5 nm) device results in a photoresponsivity improvement from 3425 A/W up to 7673 A/W, and we clearly probe the primary reason for the distinct modulation results between the 5 and 11 nm C 60 devices. In addition, the tuneable bandwidth of the infrared response from 10 to 3 × 10 3 Hz under visible light modulation is explored. Such distinct types of optical modulation phenomena and logical photocurrent inversion characteristics pave the way for future tuneable logical photocurrent switching devices and high-performance phototransistors with vertical graphene heterojunction structures.