Photodetectors based on two-dimensional
materials and their van
der Waals (vdW) heterojunctions usually have excellent optoelectronic
performance and great potential applications. Herein, gallium (Aladdin,
particles, 99.999% trace metal basis), selenium (Aladdin, powder,
99.999% trace metal basis), and iodine (Alfa Aesar, 99.999% trace
metal basis) are the raw materials for the growth of gallium selenide
(GaSe) single crystals by the chemical vapor transport method, in
which iodine is the transport agent. Subsequently, GaSe nanoflakes
are exfoliated from the grown bulk GaSe crystals by mechanical exfoliation.
The n-Si/p-GaSe van der Waals vertical heterojunctions have been designed
and fabricated for photodetection, which show good characteristics
including a high responsivity of 1.74 A/W and a fast response/recovery
time of 48 μs/88 μs under zero bias owing to their type-II
band structure and built-in electric field. The results indicate that
n-Si/p-GaSe vdW vertical heterojunctions are promising candidates
in future ultrafast optoelectronic devices.