High-performing MoS2-embedded Si photodetector

Transition metal dichalcogenides (TMDs) are a new class of materials that replace advanced functional materials like graphene, CNT etc., in photovoltaics and sensors. In the present work, the 2-dimensional tri-layer MoS2 is applied for high-performing photodetector. Here, the conventional n-doped p-type Si (n-Si/p-Si) was coated with tri-layer MoS2 film using CVD method. HRTEM reveals the presence of tri-layer with highly ordered lattice planes. Characteristic peaks of Mo and S are obtained in XPS profile. Due to spin-orbit coupling, the 3d band of Mo and 2p band of S are split into two states. Raman spectrum of MoS2 film shows two peaks, corresponding to its in-plane and out-of-plane vibrational modes. The wave number difference between these modes is measured as 22.97 cm−1, which ensures that there are three layers in MoS2 film. The splitting of valence band generates multiple excitons which are marked as A and B in the absorption profile. The excitonic transition corresponds to the direct band gap of MoS2 (ie., 1.9 eV). The prepared MoS2/n-Si/p-Si photodetector includes two rectifying junctions with considerable built-in potentials. A high rectification ratio was measured as 51.37 to ensure the quality junction formation. The photoresponse ratio of the MoS2/n-Si/p-Si photodetector was obtained as 58.74 to confirm the quality junction formation between MoS2 and Si with high detectivity of 5.42 × 1014 Jones. Moreover, the extremely fast rise and fall times of 33 µs and 30 µs were achieved without any external bias application. The functional use of MoS2 window design would provide the high potential for the enhanced photoelectric devices, such as photodetectors and solar cells.