Two-step growth of β-Ga_(2)O_(3) on c-plane sapphire using MOCVD for solar-blind photodetector

In this work,a two-step metal organic chemical vapor deposition(MOCVD)method was applied for growingβ-Ga_(2)O_(3) film on c-plane sapphire.Optimized buffer layer growth temperature(T_(B))was found at 700℃ and theβ-Ga_(2)O_(3) film with full width at half maximum(FWHM)of 0.66°was achieved.A metal−semiconductor−metal(MSM)solar-blind photodetector(PD)was fabricated based on theβ-Ga_(2)O_(3) film.Ultrahigh responsivity of 1422 A/W@254 nm and photo-to-dark current ratio(PDCR)of 10^(6) at 10 V bias were obtained.The detectivity of 2.5×10^(15) Jones proved that the photodetector has outstanding performance in detecting weak signals.Moreover,the photodetector exhibited superior wavelength selectivity with rejection ratio(R_(250 nm)/R_(400 nm))of 105.These results indicate that the two-step method is a promising approach for preparation of high-qualityβ-Ga_(2)O_(3)films for high-performance solar-blind photodetectors.

75 GHz germanium waveguide photodetector with 64 Gbps data rates utilizing an inductive-gain-peaking technique

High-performance germanium(Ge)waveguide photodetectors are designed and fabricated utilizing the inductivegain-peaking technique.With the appropriate integrated inductors,the 3-dB bandwidth of photodetectors is significantly improved owing to the inductive-gain-peaking effect without any compromises to the dark current and optical responsivity.Measured 3-dB bandwidth up to 75 GHz is realized and clear open eye diagrams at 64 Gbps are observed.In this work,the relationship between the frequency response and large signal transmission characteristics on the integrated inductors of Ge waveguide photodetectors is investigated,which indicates the high-speed performance of photodetectors using the inductive-gainpeaking technique.

Comparative transcriptome analysis of abalone Haliotis discus hannai with green and gray egg colors

Haliotis discus hannai is an important marine economic species in China.Its egg color was found to be associated with economic traits,which provides a new idea for breeding.However,the molecular mechanism of the egg-color formation has not been reported.Thus,the pigment composition and comparative transcriptome analyses of H.discus hannai with green and gray egg color were conducted using high-performance liquid chromatography(HPLC)and RNA-Seq methods.Results show that individuals with green and gray eggs both possess the fucoxanthin.Lutein existed in gray-egged individuals,but not in green-egged individuals.In transcriptome analysis,272310 unigenes were received from 461162 transcripts with a mean length of 985 bp and N50 of 1524 bp,respectively.A total of 185 unigenes were identifi ed as diff erentially expressed genes(DEGs).The DEGs involved in“fl avin-containing compound metabolic process”,“melanosome”,“glutathione metabolism”,and“cytochrome b6f complex”were likely related to the formation of the egg color.Our results provide foundational information for the functional analysis of egg-color related genes and are benefi cial to the selective breeding of H.discus hannai.

980 nm Near-Infrared Light-Emitting Diode Using All-Inorganic Perovskite Nanocrystals Doped with Ytterbium Ions

All-inorganic perovskite(CsPbX3)nanocrystals(NCs)have recently been widely investigated as versatile solution-processable light-emitting materials.Due to its wide-bandgap nature,the all-inorganic perovskite NC Light-Emitting Diode(LED)is limited to the visible region(400-700 nm).A particularly difficult challenge lies in the practical application of perovskite NCs in the infrared-spectrum region.In this work,a 980 nm NIR all-inorganic perovskite NC LED is demonstrated,which is based on an efficient energy transfer from wide-bandgap materials(CsPbCl3 NCs)to ytterbium ions(Yb3+)as an NIR emitter doped in perovskite NCs.The optimized CsPbCl3 NC with 15 mol%Yb3+doping concentration has the strongest 980 nm photoluminescence(PL)peak,with a PL quantum yield of 63%.An inverted perovskite NC LED is fabricated with the structure of ITO/PEDOT:PSS/poly-TPD/CsPbCl3:15 mol%Yb3+NCs/TPBi/LiF/Al.The LED has an External Quantum Efficiency(EQE)of 0.2%,a Full Width at Half Maximum(FWHM)of 47 nm,and a maximum luminescence of 182 cd/m?.The introduction of Yb3+doping in perovskite NCs makes it possible to expand its working wavelength to near-infrared band for next-generation light sources and shows potential applications for optoelectronic integration.

High-speed GeSn resonance cavity enhanced photodetectors for a 50 Gbps Si-based 2 μm band communication system

Expanding the optical communication band is one of the most effective methods of overcoming the nonlinear Shannon capacity limit of single fiber.In this study,GeSn resonance cavity enhanced(RCE)photodetectors(PDs)with an active layer Sn component of 9%–10.8%were designed and fabricated on an SOI substrate.The GeSn RCE PDs present a responsivity of 0.49 A/W at 2μm and a 3-dB bandwidth of approximately 40 GHz at 2μm.Consequently,Si-based 2μm band optical communication with a transmission rate of 50 Gbps was demonstrated by using a GeSn RCE detector.This work demonstrates the considerable potential of the Si-based 2μm band photonics in future high-speed and high-capacity optical communication.

Horizontal GeSn/Ge multi-quantum-well ridge waveguide LEDs on silicon substrates

A horizontal p-i-n ridge waveguide emitter on a slion(100)substrate with a Gen,g1Sno.c9/Ge multi quantum-well(MQW)active layer was fabricated by molecular beam epitaxy.The device structure was designed to reduce light absorption of metal electrodes and improve injection efficiency.Electroluminescence(EL)at a wavelength of 2160 nm was observed at room temperature.Theoretical calculations indicate that the emission peak corresponds well to the direct bandgap transition(nr-mHr).The light output power was about 2.0μW with an injection current density of 200 kA/cm^2.These results show that the horizontal GeSn/Ge MQW ridge waveguide emiters have great pros-pects for group-IV light sources.

Sn content gradient GeSn with strain controlled for high performance GeSn mid-infrared photodetectors

GeSn detectors have attracted a lot of attention for mid-infrared Si photonics,due to their compatibility with Si complementary metal oxide semiconductor technology.The GeSn bandgap can be affected by Sn composition and strain,which determines the working wavelength range of detectors.Applying the Sn content gradient GeSn layer structure,the strain of GeSn can be controlled from fully strained to completely relaxed.In this work,the strain evolution of GeSn alloys was investigated,and the effectiveness of gradually increasing Sn composition for the growth of high-Sn-content GeSn alloys was revealed.Relaxed GeSn thick films with Sn composition up to 16.3%were grown,and GeSn photodetectors were fabricated.At 77 K,the photodetectors showed a cutoff wavelength up to 4.2μm and a peak responsivity of 0.35 A/W under 1 V at 2.53μm.These results indicate that GeSn alloys grown on a Sn content gradient GeSn structure have promising application in mid-infrared detection.