Abstract Two-dimensional (2D) materials can be implemented in several functional devices for future optoelectronics and electronics applications. Remarkably, recent research on p–n diodes by stacking 2D materials in heterostructures or homostructures (out of plane) has been carried out extensively with novel designs that are impossible with conventional bulk semiconductor materials. However, the insight of a lateral p–n diode through a single nanoflake based on 2D material needs attention to facilitate the miniaturization of device architectures with efficient performance. Here, we have established a physical carrier-type inversion technique to invert the polarity of MoTe₂-based field-effect transistors (FETs) with deep ultraviolet (DUV) doping in (oxygen) O₂ and (nitrogen) N₂ gas environments. A p-type MoTe₂ nanoflake transformed its polarity to n-type when irradiated under DUV illumination in an N₂ gaseous atmosphere, and it returned to its original state once irradiated in an O₂ gaseous environment. Further, Kelvin probe force microscopy (KPFM) measurements were employed to support our findings, where the value of the work function changed from ∼4.8 and ∼4.5 eV when p-type MoTe₂ inverted to the n-type, respectively. Also, using this approach, an in-plane homogeneous p–n junction was formed and achieved a diode rectifying ratio (I_f/I_r) up to ∼3.8 × 10⁴. This effective approach for carrier-type inversion may play an important role in the advancement of functional devices.