Broadband photodetector based on MoS₂/Ge heterojunction for optoelectronic applications

In this work, we demonstrate high quality MoS₂/i-Ge heterojunction photodetector (PD) and its optoelectrical properties are analyzed over a broad spectral range which is compared with the conventional Ge Schottky PD. The MoS₂/i-Ge heterojunction PD was highly sensitive in the broadband range from 300 nm to 1700 nm, having a responsivity of 0.7 A/W, the quantum efficiency of 56.1% against 0.55 A/W and 44.4% for the conventional Ge Schottky PD at the incident wavelength of 1550 nm. For the visible light range, heterojunction PD exhibited a much higher responsivity and quantum efficiency of >0.3 A/W and ∼60%, respectively than conventional Ge Schottky PD. The improvement of Schottky PD and heterojunction PD is analyzed using the photocurrent mapping method. Finally, heterojunction PDs exhibited excellent photo-responsive switching properties. The photocurrent of MoS₂/i-Ge heterojunction PDs shows superior performance than Ge Schottky PDs for increased wavelength and optical powers. These results imply that MoS₂/Ge heterojunction PD may have great potential for broadband light detection applications as high-performance devices.