Engineering Ultrafast Carrier Dynamics at the Graphene/GaAs Interface by Bulk Doping Level

Abstract

Carrier dynamics, the most fundamental process in electronics and optoelectronics, has drawn great attentions owing to its crucial role in property engineering of materials. Exploration and regulation of carrier dynamics are essential for designing devices with specific functions and optimizing their performances. However, the lack of conventional tools with simultaneous ultrafast temporal and ultrasmall spatial resolution has impeded direct observation and manipulation of carrier dynamics at both the femtosecond and nanometer scale. In this study, the direct observation and modulation of ultrafast carrier dynamics at the graphene/gallium arsenide (GaAs) interface is achieved by tuning the doping level of bulk GaAs. This successful characterization is performed using advanced in situ photoemission electron microscopy combined with the ultrafast pump–probe technique. It is found that a change in the doping level in GaAs can change its band bending and switch the hot‐carrier transfer direction at the graphene/GaAs interface with a lifetime reduction of nearly six times. This work paves the way of engineering ultrafast carrier dynamics at 2D interfaces by modifying the 3D bulk properties, and also provides a platform for fundamental studies of ultrafast physics with high spatial resolution.

Relaxation and transfer of photoexcited electrons at a coplanar few-layer 1 T′/2H-MoTe2 heterojunction

“…In contrast, the time-resolved photoemission electron microscopy (TR-PEEM) method can simultaneously access the evolution of electrons on the time, space, and energy, providing a direct way to image the electrons' behavior at the nanoscale. Recently, the TR-PEEM technique has been applied to image the dynamics of surface plasmon [14][15][16][17][18][19][20][21][22][23] , the transport and recombination of carriers in bulk [24][25][26][27] , atomically thin semiconductors [28][29][30][31] , and vertical type-II semiconductor heterostructure 29 . Lateral modulation of electronic and optical properties of the in-plane structures is necessary for planar devices with high-density integration potentials in modern electronics 10 .…”

Direct Observation of Photoexcited Electron Dynamics in Organic Solids Exhibiting Thermally Activated Delayed Fluorescence via Time‐Resolved Photoelectron Emission Microscopy

“…The detection of such excited species is generally difficult even when using a transient absorption spectroscopic (TAS) technique, which is often employed to study optically dark excitonic species, including ionic ones. [28] In this study, we aimed to clarify the dynamics of the excited electrons in the TADF process of a 4CzIPN solid-state film, employing time-resolved photoemission electron microscopy (TR-PEEM) [29][30][31][32][33][34][35][36] (Figure 1a) and comparing it with TR-PL. A significant advantage of the TR-PEEM technique is the high sensitivity for the photoelectron signal.…”

“…In this study, we aimed to clarify the dynamics of the excited electrons in the TADF process of a 4CzIPN solid‐state film, employing time‐resolved photoemission electron microscopy (TR‐PEEM) [ 29–36 ] (Figure 1a) and comparing it with TR‐PL. A significant advantage of the TR‐PEEM technique is the high sensitivity for the photoelectron signal.…”

Heterointerface-Enhanced Ultrafast Optical Switching via Manipulating Metamaterial-Induced Transparency in a Hybrid Terahertz Graphene Metamaterial

“…2 It can also exhibit fascinating optical properties, 3 such as quantum constant transparency in the visible−infrared region, 4 giant broad-band nonlinear optical absorption, 5 and engineered ultrafast carrier dynamics for the promising applications in the next generation of optoelectronic devices. 6,7 Optical absorption in graphene involves interband transitions dominating at optical and near-infrared wavelengths while intraband transitions occur upon interaction with lowenergy photons in the far-infrared and terahertz (THz) region. 8 Subsequently, THz modulators based on intraband carrier absorption of graphene have been intensively investigated.…”

“…Since the first successful fabrication in 2004, graphene with hexagonal carbon lattice has become a promising material for technological applications owing to its remarkable properties, which include high carrier mobility, high mechanical strength, and good stability . It can also exhibit fascinating optical properties, such as quantum constant transparency in the visible–infrared region, giant broad-band nonlinear optical absorption, and engineered ultrafast carrier dynamics for the promising applications in the next generation of optoelectronic devices. , Optical absorption in graphene involves interband transitions dominating at optical and near-infrared wavelengths while intraband transitions occur upon interaction with low-energy photons in the far-infrared and terahertz (THz) region . Subsequently, THz modulators based on intraband carrier absorption of graphene have been intensively investigated. , Especially, the graphene metamaterial integrated devices are exploited to manipulate electromagnetic waves combined with the excellent properties and novel functionalities of metamaterials. − Such hybrid structures with optically and electrically controlled methods can realize amplitude modulation, phase control, the persistent photonic memory effect, extraordinary transmission, dynamic THz wavefront modulation, and near-field imaging .…”