Aluminum gallium nitride (AlGaN) metal–semiconductor–metal photodetectors were successfully fabricated with different contact materials and structures and were tested with ultrafast lasers. The experimental results were compared with the finite element simulations based on APSYS and showed consistent trend with respect to the device I–V properties and response behaviors. Persistent photoconductivity (PPC) was observed for devices with both gold and aluminum contacts and various structures, and the decay time can be longer than 10 ms. The response time and responsivity were found to be affected by the bias voltage, operating temperature, and incident power. The mechanism behind the long decay time is analyzed from the perspective of the materials properties and factors influencing the decay time are examined. The nature of the metal–semiconductor contact is studied to help understand the PPC effect, and the contact showed ohmic-like behavior.

Atomically thin transition metal dichalcogenides (TMDCs), such as WS2 and MoS2, have opened up new opportunities for the next generation of optoelectronics owing to their unique properties such as optical transparency, high carrier mobility, widely tunable band gap, and strong light–matter interaction. The photodetection performance relies primarily on the light absorption efficiency and separation efficiency of photoexcited electron–holes. The photodetectors with all broadband response, high photoconductive gain, high response speed, and high detectivity is arduous challenge to realize using one photo-active material. Building of photodetectors composed of two or more light absorber materials of different band gaps was an efficient route to realize high performance light detection. The application of a thin sensitizing layer atop the TMDCs has proven to be a viable route to improve the photodetection performance due to the efficient charge separation at the interface, and fast charge transfer process due to the high carrier mobility. In this article, we review the progress made toward hybrid photodetector based on TMDCs with various sensitizers from metal to large band-gap semiconductor in architectures from zero-dimensional quantum dot to two-dimensional crystal.