Interface Properties Probed by Active THz Surface Emission in Graphene/SiO₂/Si Heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Graphene/semiconductor heterostructures offer superior electronic and optoelectronic properties.
• Traditional methods provide limited insight into interfacial characteristics.
• Understanding these interfaces is key to advancing device performance.

Purpose of the Study:

• To introduce active THz surface emission spectroscopy for evaluating graphene/semiconductor interfaces.
• To investigate interfacial properties such as built-in potential and charge detrapping.
• To demonstrate THz spectroscopy's potential for graphene-based device analysis.

Main Methods:

• Utilized active THz surface emission spectroscopy on graphene/SiO2/Si (Gr/SiO2/Si) heterostructures.
• Analyzed interface electric-field-induced optical rectification (EFIOR) under varying gate voltages.
• Performed time-dependent THz generation measurements.

Main Results:

• Identified an intrinsic built-in potential of -0.15 V at the Gr/SiO2/Si interface.
• Observed significant THz intrinsic modulation (44% positive, 70% negative) due to the interface depletion layer.
• Deduced the charge detrapping decay time constant using time-resolved THz measurements.

Conclusions:

• Active THz surface emission spectroscopy provides intuitive insights into graphene/semiconductor interfacial states (depletion, weak/strong inversion).
• The technique is effective for characterizing built-in potential and charge dynamics.
• Demonstrated potential for efficient THz modulation and enhanced THz emission in heterostructures.