Flexible Phototransistors Based on Single‐Crystalline Silicon Nanomembranes

Abstract

In this work, flexible phototransistors with a back gate configuration based on transferrable single‐crystalline Si nanomembrane (Si NM) have been demonstrated. Having the Si NM as the top layer enables full exposure of the active region to an incident light and thus allows for effective light sensing. Flexible phototransistors are performed in two operation modes: 1) the high light detection mode that exhibits a photo‐to‐dark current ratio of 105 at voltage bias of VGS < 0.5 V, and VDS = 50 mV and 2) the high responsivity mode that shows a maximum responsivity of 52 A W−1 under blue illumination at voltage bias of VGS = 1 V, and VDS = 3 V. Due to the good mechanical flexibility of Si NMs with the assistance of a polymer layer to enhance light absorption, the device exhibits stable responsivity with less than 5% of variation under bending at small radii of curvatures (up to 15 mm). Overall, such flexible phototransistors with the capabilities of high sensitivity light detection and stable performance under the bending conditions offer great promises for high‐performance flexible optical sensor applications, with easy integration for multifunctional applications.

Semiconductor Nanomembrane-Based Light-Emitting and Photodetecting Devices

“…The other is to take advantage of the flexible mechanical property to realize bendable phototransistors and photodetectors [25,[41][42][43] and light-emitting diodes (LEDs) [44] by transfer printing a very thin membrane layer onto a plastic substrate.…”

“…Pioneered by Rogers et al, a polydimethylsiloxane (PDMS) stamp-assisted transfer printing process has been used to transfer a variety of crystalline semiconductor NMs on different foreign host substrates. This heterogeneous materials stack could be integrated with Si and flexible substrate applications [25][26][27][28][29][30][31][32][33].…”

“…Up to now, semiconductor NMs have been successfully transferred onto numerous kinds of substrates, including glass [34][35][36], plastics [24][25][26][27], biodegradable nanofibril paper [37], etc.…”

High-performance flexible BiCMOS electronics based on single-crystal Si nanomembrane

“…[18][19][20] Thus, it enables us to demonstrate high performance flexible CMOS TFTs such as flexible RF TFTs, high sensitivity light sensors, bio-medical devices, and environment-friendly devices. [12][13][14][15][16][21][22][23][24] Although these demonstrations were very successful on their own, all of them have been fabricated using CMOS technology that is inadequate to handle high power signals or to satisfy more functionally advanced flexible electronics.…”

“…[9][10][11][12][13] Up to date, all the Si-based thinfilm transistors (TFTs) have been realized with CMOS technology because of their simple structure and process. [12][13][14] However, as more functions are required in future flexible electronic applications (i.e., advanced bioelectronic systems or flexible wireless power applications), [15][16][17] an integration of functional devices in one flexible substrate is needed to handle complex signals and/or various power levels. In light of the development in and wide applications of the rigid-chip-based semiconductor transistors, a mechanically flexible BiCMOS platform will also be able to open a new pathway in fulfilling the needs of advanced flexible electronics.…”