Electric-field tunable Type-I to Type-II band alignment transition in MoSe₂/WS₂ heterobilayers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Semiconductor heterojunctions are fundamental to electronics, with properties dictated by interface band alignment (type-I, -II, or -III).
• Controlling band alignment within a single material is highly desirable for advanced device functionalities.

Purpose of the Study:

• To demonstrate electrically tunable band alignment transitions in MoSe2/WS2 heterobilayers.
• To investigate the impact of electric fields on luminescence and photocurrent characteristics.
• To explore the potential for novel optoelectronic devices based on van der Waals heterostructures.

Main Methods:

• Fabrication of MoSe2/WS2 heterobilayers.
• Investigation of luminescence and photocurrent under varying electric fields.
• Analysis of band alignment transitions between type-I and type-II.

Main Results:

• Intrinsic heterobilayers exhibit type-I band alignment with dominant intralayer exciton luminescence.
• An applied electric field induces a transition to type-II band alignment, enhancing interlayer exciton luminescence.
• Interlayer excitons trap carriers, suppressing photocurrent and leading to nonlinear current-voltage characteristics.

Conclusions:

• Electrical control over band alignment and interlayer excitons is achieved in MoSe2/WS2 heterobilayers.
• This control enables manipulation of carrier dynamics and device performance.
• The findings pave the way for versatile optoelectronic devices utilizing van der Waals heterostructures.