A 4×4 metal-semiconductor-metal rectangular deep-ultraviolet detector array of Ga_(2)O_(3)photoconductor with high photo response

A 4×4 beta-phase gallium oxide(β-Ga_(2)O_(3))deep-ultraviolet(DUV)rectangular 10-fingers interdigital metalsemiconductor-metal(MSM)photodetector array of high photo responsivity is introduced.The Ga2O_(3)thin film is prepared through the metalorganic chemical vapor deposition technique,then used to construct the photodetector array via photolithography,lift-off,and ion beam sputtering methods.The one photodetector cell shows dark current of 1.94 p A,phototo-dark current ratio of 6×10_(7),photo responsivity of 634.15 A·W^(-1),specific detectivity of 5.93×1011cm·Hz1/2·W^(-1)(Jones),external quantum efficiency of 310000%,and linear dynamic region of 108.94 d B,indicating high performances for DUV photo detection.Furthermore,the 16-cell photodetector array displays uniform performances with decent deviation of 19.6%for photo responsivity.

Review of gallium oxide based field-effect transistors and Schottky barrier diodes

Gallium oxide(Ga_2O_3), a typical ultra wide bandgap semiconductor, with a bandgap of ~4.9 e V, critical breakdown field of 8 MV/cm, and Baliga's figure of merit of 3444, is promising to be used in high-power and high-voltage devices.Recently, a keen interest in employing Ga_2O_3 in power devices has been aroused. Many researches have verified that Ga_2O_3 is an ideal candidate for fabricating power devices. In this review, we summarized the recent progress of field-effect transistors(FETs) and Schottky barrier diodes(SBDs) based on Ga_2O_3, which may provide a guideline for Ga_2O_3 to be preferably used in power devices fabrication.

High-responsivity solar-blind photodetector based on MOCVD-grown Si-dopedβ-Ga_(2)O_(3)thin film

Si-dopedβ-Ga_(2)O_(3)films are fabricated through metal-organic chemical vapor deposition(MOCVD).Solar-blind ultraviolet(UV)photodetector(PD)based on the films is fabricated by standard photolithography,and the photodetection properties are investigated.The results show that the photocurrent increases to 11.2 mA under 200μW·cm^(-2)254 nm illumination and±20 V bias,leading to photo-responsivity as high as 788 A·W^(-1).The Si-dopedβ-Ga2O3-based PD is promised to perform solar-blind photodetection with high performance.

Synthesis of free-standing Ga_2O_3 films for flexible devices by water etching of Sr_3Al_2O_6 sacrificial layers

Flexible electronic devices have attracted much attention due to their practical and commercial value. Integration of thin films with soft substrate is an effective way to fabricate flexible electronic devices. Ga_2O_3 thin films deposited directly on soft substrates would be amorphous mostly. However, the thickness of the thin film obtained by mechanical exfoliation method is difficult to control and the edge of the film is fragile and easy to be damaged. In this work, we fabricated free-standing Ga_2O_3 thin films using the water-soluble perovskite Sr_3Al_2O_6 as a sacrificial buffer layer. The obtained Ga_2O_3 thin films were polycrystalline. The thickness and dimension of the films were controllable. A flexible Ga_2O_3solar-blind UV photodetector was fabricated by transferring the free-standing Ga_2O_3 film on a flexible polyethylene terephthalate substrate. The results displayed that the photoelectric performances of the flexible Ga_2O_3 photodetector were not sensitive to bending of the device. The free-standing Ga_2O_3 thin films synthesized through the method described here can be transferred to any substrates or integrated with other thin films to fabricate electronic devices.

Rectifying characteristics and solar-blind photoresponse in β-Ga2O3/ZnO heterojunctions

Heterojunctions composed ofβ-Ga2 O3 and ZnO films are fabricated on sapphire substrates by using the laser molecular beam epitaxy method.The heterojunction possesses excellent rectifying characteristics with an asymmetry ratio over 105.Prominent solar-blind photoresponse effect is also observed in the formed heterojunction.The photodetector exhibits a self-powered behavior with a fast response speed(rise time and decay time are 0.035 s and 0.032 s respectively)at zero bias.The obtained high performance can be related to the built-in field driven photogenerated electron-hole separation.

A broadband self-powered UV photodetector of aβ-Ga2O3/γ-CuI p–n junction

The symmetric Ti/Au bi-layer point electrodes have been successfully patterned on theβ-Ga;O;films which are prepared by metal–organic chemical vapor deposition(MOCVD)and theγ-Cu I films which are prepared by spin-coating.The fabricated heterojunction has a large open circuit voltage(Voc)of 0.69 V,desired for achieving self-powered operation of a photodetector.Irradiated by 254-nm ultraviolet(UV)light,when the bias voltage is-5 V,the dark current(Idark)of the device is 0.47 p A,the photocurrent(Iphoto)is-50.93 n A,and the photo-to-dark current ratio(Iphoto/Idark)reaches about 1.08×10;.The device has a stable and fast response speed in different wavelengths,the rise time(τr)and decay time(τd)are 0.762 s and 1.741 s under 254-nm UV light illumination,respectively.While theτr andτd are 10.709 s and7.241 s under 365-nm UV light illumination,respectively.The time-dependent(I–t)response(photocurrent in the order of10-10 A)can be clearly distinguished at a small light intensity of 1μW·cm;.The internal physical mechanism affecting the device performances is discussed by the band diagram and charge carrier transfer theory.

Self-powered solar-blind photodiodes based on EFG-grown(100)-dominant β-Ga_(2)O_(3) substrate

We report the edge-defined-film-fed(EFG)-grown β-Ga_(2)O_(3)-based Schottky photodiodes.The device has a reverse leakage current of ~nA and a rectified ratio of ~10^(4) at ±5 V.In addition,the photodiode detector shows a dark current of 0.3 pA,a photo-responsivity(R) of 2.875 mA/W,a special detectivity(D*) of 10^(10) Jones,and an external quantum efficiency(EQE) of 1.4% at zero bias,illustrating a self-powered operation.This work may advance the development of the Ga_(2)O_(3)-based Schottky diode solar-blind photodetectors.

Pollen and Plant Reproduction Biology： Blooming from East to West

The idea of assembling a Special Issue on Pollen Tube and Reproduction in Molecular Plant was conceived during the organization of the 2012 Pollen Biology International Symposium and Workshop held at the Shanghai Institute of Plant Physiology and Ecology （SIPPE）, Chinese Academy of Science （CAS）, 27-31 October 2012. Wei-Hua Tang of the SIPPE led the organization, with the support of Hong-Wei Xue, Director of SIPPE acting as Chair of the Organization Committee. The 2-d symposium was attended by about 100 international participants and focused on reports and discus- sions on the most recent research activities in the field. The 2-d workshop that followed provided a forum for in-depth introduction on various aspects of pollen and plant reproduc- tion biology to about 200 graduate students, postdoctoral fellows, and new investigators to the field.

High-resolution gene profiling of infection process indicates serine metabolism adaptation of Fusarium graminearum in host

Fusarium graminearum,an important fungal pathogen,can cause head blight,seedling blight and crown rot on wheat(Triticum aestivum),stalk rot and ear rot on maize(Zea mays)[1,2].Annually,billions of dollars are lost world widely because of this pathogen with the capability,not only of reducing yields,but also of produc-

What took you so long?Peptide-receptor kinase signaling mediates reproductive isolation in plants

The peptide-receptor kinase-based intercellular signaling becomes an important molecular base for various aspects of plant life activities[1],particularly exemplified in the extensive molecular interactions in the journey of pollen tube growth in pistil of flowering plants[2].Researches in the past two decades demonstrated that peptide-receptor kinase signaling complexes mediat epollen tube promotion,guidance and reception,as well as selfincompatibility and gamete fusion.A recent exciting discovery published on Science by Zhong et al.expands the biological functions of peptide-receptor kinase signaling to facilitating formation of a new plant species[3].

FERROELECTRIC SWITCHING PATH IN MONODOMAIN RHOMBOHEDRAL BiFeO_(3)CRYSTAL:A FIRST-PRINCIPLES STUDY

Based on density-functional calculations,we have studied possible ferroelectric switching path in monodomain single crystal of rhombohedral BiFeO_(3),a prototypical multiferroic compound.By carefully studying the behaviors of FeO_(3)corner-sharing double-tetrahedrons,we find abrupt changes in total energy and oxygen atomic positions,and therefore polarizations,occur in the ferroelectric switching path of rhombohedral BiFeO_(3).Detailed analyses suggest that such behavior might be caused by the frustrated magnetic ordering in the paraelectric phase of rhombohedral BiFeO_(3),where three O atoms and the Bi atom are in the same plane perpendicular to the polar-ization direction.This is supported by the fact that the ferroelectric switching for paramagnetic BiFeO_(3)is smooth and has a much lower energy barrier than that of an tiferromagnetic BiFeO_(3).