Lateral and Vertical p–n Homojunctions Formed in Few-Layer MoTe₂ with In Surface Charge-Transfer Doping

Two-dimensional (2D) layered molybdenum ditelluride (2H-MoTe2) has attracted tremendous research interest for enabling device applications with unconventional features and performance. Forming p–n homojunctions turns out to be very crucial for the device applications in photovoltaic detectors. Here, indium (In) surface electron transfer doping is found to be an efficient way to form an air-stable p–n homojunction in the MoTe2 flakes. With different thickness In layers depositing on the MoTe2, the carrier mobility of the MoTe2 flake is rationally modulated, and its electron mobility is enhanced from 0.2 to 19 cm2 V–1 s–1. The effective carrier modulation of the MoTe2 with In electron doping enables to achieve lateral and vertical p–n homojunctions formed in the flake. The photoresponsivity of the lateral photovoltaic detector is about 6 mA/W at 532 nm and 4 mA/W at 1064 nm. The photoresponsivity of the vertical device (Pt/MoTe2/In/Au) is about 125 mA/W at 532 nm and 100 mA/W at 1064 nm. These results would be beneficial for fabricating future 2D semiconductor-based optoelectronic devices.