Two-dimensional Van der Waals heterostructures provide an amazing platform to study the fundamental physics property and build optoelectrical devices because of their abundant band structures and the clean interface. In...

Molybdenum disulfide (MoS2) is natively an n-type semiconductor due to omnipresent electron-donating sulfur vacancies, indicating the synthesis of high-quality p-type semiconducting MoS2 has been challenging. Substitutional doping has been proved...

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.

Van der Waals heterojunction devices are of great significance for developing high-performance optoelectronic devices. Here, a strategy has been introduced to effectively improve the performance of devices by designing their structure, and three types of devices based on MoS2/GaSe heterojunctions were designed and fabricated. The results have demonstrated that device-III effectively decreases the recombination of the electrons in GaSe flakes by removing the non-heterojunction region and depleting the GaSe flake, which results in electron-dominated channel current and much better electrical performance than device-I and device-II, such as a larger rectification ratio of 1.6 × 105 and an ideality factor of 1.06. Furthermore, a photodetector based on device-III exhibits high performance for self-driven photodetection under 532 nm light irradiation, including a responsivity of 249 mA/W, a specific detectivity of 3.6 × 1011 Jones, an open-circuit voltage of 0.56 V, and a short response/recovery time of 10.5 μs/7.3 μs. The results introduced here provide a path to significantly improve the electrical properties of optoelectronic devices based on a 2D material heterostructure.