Graphene-PbS quantum dot hybrid photodetectors from 200 mm wafer scale processing

Abstract

A 200 mm processing platform for the large-scale production of graphene field-effect transistor-quantum dot (GFET-QD) hybrid photodetectors is demonstrated. A comprehensive statistical analysis of the electrical data revealed a high yield (96%) and low variation in the 200 mm scale fabrication. The GFET-QD devices deliver responsivities of 10⁵ to 10⁶ V/W in the wavelength range from 400 to 1800 nm with a response time of 10 ms. The spectral sensitivity compares well to that obtained via similar GFET-QD photodetectors. The device concept enables gate-tunable suppression or enhancement of the photovoltage, which may be exploited for electric shutter operation by toggling between the signal capture and shutter states. The devices show good stability over a wide operation range. Furthermore, an integration solution with complementary metal-oxide-semiconductor technology is presented to realize image-sensor-array chips and a proof-of-concept image system. This work demonstrates the potential for the volume manufacture of infrared photodetectors for a wide range of imaging applications.

Fig. 1

(a) Schematic of the device architecture of the tandem GFET‒QD photodetector. (b) Schematic energy band diagram upon illumination. (c) Top-view optical microscope image of the tandem GFET‒QD photodetector device. (d) Fabrication flow of the GFET-QD photodetector, including the key steps of graphene transfer, patterning, contacting, QD deposition, encapsulation, and packaging. (e) As-fabricated 200 mm wafer (left) and later diced, wire-bonded, and packaged single-pixel photodetector in a hermetically sealed semiconductor package (right). (f–i) 200 mm wafer scale statistics of the electric metrics of encapsulated GFETs. Box-whisker plots of (f) Dirac points and hysteresis, (g) field effect mobility, (h) contact resistance, and (i) sheet resistance of the GFETs. Inset in (f): a photo of the 200 mm wafer after fabrication.

Fig. 2

Electro-optical response of the GFET-QD photodetector. (a) Photovoltage emerging at the graphene‒QD junction shown against the I_ds-V_gs curve of a GFET device (V_ds = 0.5 V) with an irradiance level < 10^–3 W/m². (b) Photoresponse curves of the photodetector as a function of chopping frequency, with wavelengths of 520 and 1550 nm (V_ds = 0.5 V, V_gs = -1.0 V). (c) Photoswitching behavior of the photodetector toward pulsed light illumination at a wavelength of 1550 nm, light intensity of 0.7 W/m², V_gs = − 1.0 V and V_ds = 0.5 V. (d) Photoresponse curves of the photodetector as a function of wavelength, with frequencies of 10 Hz and 100 Hz (V_ds = 0.5 V, V_gs = − 1.0 V).

Fig. 3

Tandem GFET-QD image sensor. (a) Schematic of a single-pixel photodetector device prior to hermetic sealing into a metal T0-8 semiconductor package with a sapphire window. (b) A single pixel photodetector after hermetic sealing of the sapphire window and connection to a dedicated readout electronics board. (c) Photograph of a few-pixel GFET array fabricated directly on an ASIC and subsequently wire bonded and hermetically sealed into a QFN package. Corresponding photoresponse of the few-pixel array measured through the ASIC at back gate voltages of V_gs = (d) − 1.4 V and (e) − 0.5 V, λ = 1550 nm, P = 0.7 W/m², V_ds = 0.5 V. Units are arbitrary digital values from the DAC output of the ROIC.