High-speed nonlinear focus-induced photoresponse in amorphous silicon photodetectors for ultrasensitive 3D imaging applications
Andreas Bablich, Maurice Müller, Paul Kienitz, Rainer Bornemann, Charles Otieno Ogolla, Benjamin Butz, Bhaskar Choubey, P. Haring Bolívar
Abstract
Abstract A large and growing number of applications benefit from simple, fast and highly sensitive 3D imaging sensors. The Focus-Induced Photoresponse (FIP) can achieve 3D sensing functionalities by simply evaluating the irradiance dependent nonlinear sensor response in defect-based materials. Since this advantage is intricately associated to a slow response, the electrical bandwidth of present FIP detectors is limited to a few $${\text{kHz}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>kHz</mml:mtext> </mml:math> only. The devices presented in this work enable modulation frequencies of 700 kHz and beat frequency detection up to at least 3.8 MHz, surpassing the bandwidth of reported device architectures by more than two orders of magnitude. The sensors achieve a SNR of at least $$\sim 53\;{\text{dB}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>53</mml:mn> <mml:mspace/> <mml:mtext>dB</mml:mtext> </mml:mrow> </mml:math> at $$115\;{\text{cm}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>115</mml:mn> <mml:mspace/> <mml:mtext>cm</mml:mtext> </mml:mrow> </mml:math> and a DC FIP detection limit of 0.6 µW/mm 2 . The mature and scalable low-temperature a-Si:H process technology allows operating the device under ambient air conditions waiving additional back-end passivation, geometrical fill factors of $$100\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>100</mml:mn> <mml:mo>%</mml:mo> </mml:mrow> </mml:math> and tailoring the FIP towards adjustable 3D sensing applications.