研究目的
Investigating the carrier lifetimes in graphene/hBN van der Waals heterostructures under mid-infrared illumination for potential applications in THz lasing and photodetection.
研究成果
The study demonstrates ultra-long carrier lifetimes in graphene/hBN heterostructures under mid-infrared illumination, highlighting the potential for THz lasing and photodetection applications. It also shows the ability to control carrier lifetimes through bias and optical power, switching between Auger recombination and HPhP emission processes.
研究不足
The study is limited by the sample dimensions and the diffraction-limited spot size for mid-infrared light, which affects the photoconductive gain. Additionally, the inhomogeneities of the Fermi level within the sample area due to charge puddles may underestimate the carrier recombination times.
1：Experimental Design and Method Selection:
The study uses mid-infrared photoconductivity measurements to investigate carrier lifetimes in graphene/hBN Zener-Klein transistors. The methodology involves continuous mid-infrared laser excitation and transport measurements under controlled doping conditions.
2：Sample Selection and Data Sources:
The samples consist of hBN-encapsulated exfoliated single-layer graphene with dimensions L × W = 20 μm × 10.4 μm, deposited on a Ni bottom gate electrode and equipped with Cr/Au edge contacts.
3：4 μm, deposited on a Ni bottom gate electrode and equipped with Cr/Au edge contacts.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: A CO2 laser delivering 10.6 μm wavelength light modulated at 5 kHz, a liquid He cryostat with ZnSe optical window, and a lock-in amplifier for photocurrent signal measurement.
4：6 μm wavelength light modulated at 5 kHz, a liquid He cryostat with ZnSe optical window, and a lock-in amplifier for photocurrent signal measurement.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The experiment involves focusing the laser light on the sample using an aspheric Ge lens, placing the sample within the cryostat, and measuring the photocurrent signal with a lock-in amplifier.
5：Data Analysis Methods:
The analysis includes extracting carrier lifetimes from photocurrent measurements and electrical characterization, considering the interplay between Auger recombination and HPhP emission processes.
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