Black phosphorene (BP) nanosheet, a new type of two-dimensional material with the characteristics of ultra-thin structure and ultra-fast conductivity, has achieved wide attention of researchers in basic research and technical application fields. However, the nonlinear optical (NLO) absorption of black phosphorene is not strong enough to meet the application requirements of NLO devices. Interconnecting black phosphorene with nano-materials is an effective method to improve its NLO effect. In this work, Ag nanoparticles were anchored on the surface of BP nanosheets by thermochemical method and the BP/Ag nanohybrids (NHs) were successfully formed, which is certified by TEM, XRD, Raman and XPS measurements. The covalent functionalization with Ag nanoparticles can tune the bandgap of BP nanosheets and improve their NLO response. Compared with the NLO simple addition of BP and Ag, the additional synergistic effect between them plays a major role in enhancing the NLO absorption of BP/Ag nanohybrids, and this synergistic nonlinear enhancement is closely related to the Ag concentration and the non-radiation defect density in the nanocomposites. The NLO enhancement mechanisms of extra charger transfer and local field are confirmed by femtosecond-ultrafast dynamics analysis and FDTD calculation. This work provides the new BP/Ag NH material with good optical nonlinearity and NLO mechanism discussion for potential opto-electronical applications.
The polarization-integrated infrared detector (PIID) can distinguish the intrinsic property polarization of artificial target and background, and improve the capability of target detection and recognition. In this paper, we use the finite element method (FEM) to build the physical model of long wavelength (LWIR) PIID (8-14um) detector based on InAs/GaSb II superlattices (T2SLs). Our calculation results show thate grating array period, grating line width and thickness can effectively influence the light crosstalk between adjacent pixels, which is the key to the device extinction ratio. In addition, we design micro-structure to PIID, which plays an important role in improving device extinction. As a result, the extinction ratio was improved from 75:1 to 610:1 at the wavelength of 10.9μm. The physical mechanism of suppressing extinction ratio is analyzed in detail.
Many applications such as toxic gas detection or H2S monitoring in natural gas require operation in the THz spectral region, where gas species show distinct spectral “fingerprints” that can be easily discriminated by the gas matrix background absorption features.
So far, continuous-wave THz quantum cascade lasers employed in quartz-enhanced photoacoustic (QEPAS) sensors required liquid helium-cooling systems. In this work, we demonstrated the first liquid nitrogen-cooled THz QEPAS sensor for H2S detection operated in pulsed mode and mounting a spectrophone based on a quartz tuning fork with 1.5 mm prong spacing. A sensitivity level in the part-per-billion concentration range was achieved.
Black phosphorus (BP), an emerging 2D semiconductor, bridges the energy band gap between the zero-band gap graphene and large band gaptransition metal dichalcogenides owing to its size-dependent tunable band gap. In the past few years, significant progress has been made in the structure design, growth and optical properties of BP, yet studies on the size-related nonlinear optical performance need to be carried out. To investigate the correlation between size and the nonlinear optical response, we prepared BP nanosheets and quantum dots via thermochemical method, which are determined by experimental measurements of TEM characterization. The nonlinear optical absorption of BP are enhanced 16.6 times with the size decrease, which might be attributed to the photoinduced dipole moment. Tuning the size of BP nanomaterials is a useful way to enhance the optical nonlinearity for potential applications in optical and optoelectric devices
In the past few years, significant progress has been made in the structure design, growth and nonlinear optical properties of graphene and graphene-based nanohybrids. The surface defects on the nanomaterials play an important role on the optical nonlinearity of graphene and graphene-based nanohybrids owing to a large surface-to-volume ratio in the nanomaterials. To investigate the correlation between surface defects and the synergistic nonlinear optical response in graphene-based nanocomposites, we attached CdS nanocrystals on the surface of graphene and prepared G/CdS nanohybrids and graphene nanosheets consisting of different oxygen-containing functional groups via chemical method, which are determined by experimental measurements of FTIR and XPS characterization. The nonlinear optical absorption and refraction of G/CdS nanohybrids under single pulse laser irradiation are enhanced 10.8 times with the concentration decrease of surface oxygen-containing groups, which might be attributed to the local field effects and synergetic effects stemming from charge transfer between the two components. Surface oxygen-containing defects tuned nonlinear optical absorption and refraction of graphene nanosheets are also investigated. Tuning the surface oxygencontaining defects of graphene and G/CdS nanohybrids is a useful way to enhance the optical nonlinearity for potential applications in devices.
We report on the performance of long wavelength infrared type-II InAs-based InAs/GaAsSb superlattice photodiodes grown by molecular-beam epitaxy. The detectors had a 100% cutoff wavelength of ~ 9.7 μm and a peak current responsivity of 2.16 A/W at 80 K. The dark current density at -50 mV bias was 6.4×10-4 A/cm2 and the resistance-area product at zero bias (R0A) was 36.9 Ωcm2. The black body detectivity and peak detectivity were 7.5×1010 cm Hz1/2/W and 1.97×1011 cm Hz1/2/W, respectively. The quantum efficiency at 7.6 μm was measured to be ~34%. Good agreement was achieved between the measured I-V curves and the simulated ones, and between the experimental and theoretically predicted differential resistance values. At temperatures exceeding 75 K diffusion currents dominate the device performance. In the temperature range between 65 and 75 K, the performance of the InAs-based SL photodiodes is limited by GR processes. Trap-assisted tunneling current provides a significant contribution at temperatures below 65 K, while coherent tunneling currents are not of importance.
The barrier enhanced InAs/GaSb long wavelength photodetectors were proved to have better performance. Our previous work showed a PBIN detector with an electron barrier inserted show significantly improved electrical performances compared to a PIN structure. To improve the quantum efficiency, Be-doping was employed to convert the conductivity of the long wavelength SL structure, the PN junction moves away from the B-I hetrostructure to the π-N interface which loses the barrier effect. Therefore, the hole barrier was needed to form a PBπBN structure. In this paper, both the abrupt and gradual hole barrier was designed without Al element to form a PBπBN structure. The gradual hole barrier was optimized to avoid the blocking of photo generated current, maximized the quantum efficiency. The RmaxA product of the PBπBN detector was measured to be 77 Ωcm2 and the dark current density under -0.05V bias was measured to be 8.8×10-4A/cm2 at 80K. The quantum efficiency of gradual hole barrier detector was measured to be 27.2% at 10.6 μm and the quantum efficiency was slowly decreased under reverse bias. The result shows the gradual hole barrier efficiently eliminate the peak barrier in the electron band. The peak detectivity of this graded detector is calculated to be 9.46×1010cm.Hz1/2.W-1 at 10.6 μm.
The barrier enhanced InAs/GaSb long wavelength photodetectors were designed and demonstrated in this paper. A PBIN detector with an electron barrier inserted between P type contactor and absorption region show significantly improved electrical performances compared to a PIN structure. The RmaxA product of the PBIN detector was measured to be 104 Ωcm2 at 80K and 7360 Ωcm2 at 50K. Temperature dependent measurements show that the tunneling currents dominate the dark current below 50K, the generation-recombination (GR) currents dominate from 50K to 90K, and the diffusion current dominate over 90K. The PBIN structure benefits from a lower electric field in the absorption region and therefore, suppressed the tunnel currents and GR currents. To improve the quantum efficiency, Be-doping was employed to convert the conductivity of the long wavelength SL structure, the PN junction moves away from the B-I hetrostructure to the π-N interface, which loses the barrier effect. Therefore, the hole barrier was needed to form a PBπBN structure. In this paper, hole barrier was designed without Al element to form a PBπBN structure. The RmaxA product of the PBπBN detector was measured to be 77 Ωcm2 and the dark current density under -0.05V bias was measured to be 8.8×10-4A/cm2 at 80K. The peak current responsivity at 9.8 μm was 2.15A/W and the quantum efficiency was 26.7%.
InAs/GaSb superlattices are excellent candidates for the third-generation long-wave infrared
and very-long-wave infrared photodetectors due to their special energy structure and theoretical
advantages. To realize their inherent potential, however, superlattice materials with low defect density
and improved device characteristics must be demonstrated. Here we report on the demonstration of highperformance
PBπN photodiodes based on type-II InAs/GaSb superlattices with full cut-off wavelength ~
13.0 μm operating at 77 K. Samples with migration-enhanced epitaxy for interface layers were grown by
molecular beam epitaxy on GaSb substrates and characterized by high-resolution X-ray diffraction and
atomic force microscopy. The FWHM of the 1st-order X-ray diffraction satellite peak of the absorption
layers was only 21.6". The average roughness from AFM on a 2×2 μm2 scan area was less than 0.15 nm.
Optical and electrical measurements of the photodiodes revealed high uniformity of the type-II
superlattice materials. Across the wafer, the detector structure showed a full cut-off wavelength of 13.0
μm at 77 K. The dark current density at -50 mV was 5.1×10-4 A/cm2 and the maximum resistance-area
product (RmaxA) was 128.5 Ω cm2.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.