Photosensitive Complementary Inverters Based on n‐Channel MoS₂ and p‐Channel MoTe₂ Transistors for Light‐to‐Frequency Conversion Circuits

Abstract

Photosensitive complementary inverters, composed of multilayered molybdenum disulfide (MoS2) and molybdenum ditelluride (MoTe2), are demonstrated for the applications that require low power consumption and excellent signal‐to‐noise ratio (SNR). The photosensitive characteristics of MoS2, along with the negligible photosensitivity of MoTe2, successfully render them applicable to the light‐to‐frequency conversion circuits that enable high SNR immunity. Under blue light‐emitting diodes (LEDs), the low noise margin and transition width for the voltage transfer characteristics in complementary inverters significantly improve from 1.29 to 1.49 V and 0.24 to 0.31 V, respectively, as compared with those of inverters in the dark. The experimental demonstration of photosensitive inverters and their electrical validations on proposed concepts, supported from SPICE (i.e., simulation program with integrated circuit emphasis) simulation, are systematically obtained, substantiating that this platform can be one of the core parts for future Internet of Things (IOT) applications, which simultaneously demand both ultralow power and robustness on security.

Photosensitive Complementary Inverters Composed of n‐Channel ReS2 and p‐Channel Single‐Walled Carbon Nanotube Field‐Effect Transistors

“…In addition, as per n‐channel m‐ReS 2 FETs, Figure 2c shows that current saturation behaviors for output characteristics were noticeably degraded with light illumination. As previously reported in the literature, [ 12 ] a current level and its saturation behavior in the output characteristics were important properties to determine the VTCs of inverter. Thus, reduced saturation property leads to a decrease in gains in VTCs (Figure S3, Supporting Information), which is one of the crucial factors because oscillation frequency of ROs is strongly governed by inverter gains, depending on a wavelength for the illuminated light.…”

“…In this sense, photosensitive inverters are one of the compulsory elements which lead to increase for the level of high‐end security, thereby, there has been reported for the several key research activities for the implementation of light‐to‐frequency (LTF) circuits, [ 9–12 ] which is highly beneficial for achieving significant improvement in SNR for IoT systems. However, there is still much need to be scaled down in sensor devices, leading to tremendous improvement in fulfilling density of chips for the implementation of photodetectors‐based system.…”

“…For adjustable and appropriate photosensitive LTF circuits under visible light illumination, yielding oscillation frequency modulation corresponding to the wavelength of illumination light, the one-sided photoresponsive semiconductor in complementary inverters, from only either n-channel or p-channel photoresponsivity, is highly required for achieving adequate degradation of gains for photosensitive inverters. [12] In this sense, for achieving excellently operational LTF conversion circuits, composed of serially connected odd number of complementary photosensitive inverters, sensitive photoresponsivities for n-channel of multilayered ReS 2 (m-ReS 2 ) field-effect transistors (FETs) with a condition of dullness of light responsivity for p-channel SWNT FETs are highly desirable. [16] This is attributed to achievement for fulfilling key requirements such as low-power demonstration with high span of ring oscillation frequency during visible light illumination, with high density of circuits which renders LTF circuit efficient in terms of area density associated with 2D semiconductors of DOI: 10.1002/pssr.202000420 For robustness on security and ultralow power consumption for Internet of Things (IoT) sensors, including ultraminiaturization for high chip density, 2D multilayered ReS 2 field-effect transistors (FETs) combined with photoinsensitive single-walled carbon nanotube (SWNT) FETs are demonstrated for application in light-to-frequency (LTF) conversion circuits.…”

“…The property of m-ReS 2 layer with a direct bandgap can contribute to high selectivity on discernible photoresponse between a red and a green light, respectively, as compared with other m-TMDC layers in the previous reported literature. [10][11][12] In addition, as one of the important key parameters for the application of LTF circuits, power consumption should be understood, thereby, the extracted power consumption for complementary inverters during light illumination is shown in Figure 3f, as compared with the previously reported conventional TMDC-based photosensitive inverters in the literature. [10][11][12] Overall, due to the configuration of complementary inverters, the power consumption in this article under dark condition is at least ten times low as much as that of depletion mode load-based multilayered MoS 2 inverters.…”

“…[10][11][12] In addition, as one of the important key parameters for the application of LTF circuits, power consumption should be understood, thereby, the extracted power consumption for complementary inverters during light illumination is shown in Figure 3f, as compared with the previously reported conventional TMDC-based photosensitive inverters in the literature. [10][11][12] Overall, due to the configuration of complementary inverters, the power consumption in this article under dark condition is at least ten times low as much as that of depletion mode load-based multilayered MoS 2 inverters. In addition, the lower power consumption for m-ReS 2 FETs-based complementary inverters, in particular for the wavelength larger than that of green light, is demonstrated as compared with that of complementary inverters composed of n-channel MoS 2 and p-channel MoTe 2 FETs, due to less photocurrent associated with the larger E g (%1.5 eV) for m-ReS 2 FETs as compared with m-MoS 2 (%E g ¼ 1.2 eV).…”