Facile Semiconductor p-n Homojunction Nanowires with Strategic p-Type Doping Engineering Combined with Surface Reconstruction for Biosensing Applications

Photosensors with versatile functionalities have emerged as a cornerstone for breakthroughs in the future optoelectronic systems across a wide range of applications.In particular,emerging photoelectrochemical(PEC)-type devices have recently attracted extensive interest in liquid-based biosensing applications due to their natural electrolyte-assisted operating characteristics.Herein,a PEC-type photosensor was carefully designed and constructed by employing gallium nitride(GaN)p-n homojunction semiconductor nanowires on silicon,with the p-GaN segment strategically doped and then decorated with cobalt-nickel oxide(CoNiO_(x)).Essentially,the p-n homojunction configuration with facile p-doping engineering improves carrier separation efficiency and facilitates carrier transfer to the nanowire surface,while CoNiO_(x)decoration further boosts PEC reaction activity and carrier dynamics at the nanowire/electrolyte interface.Consequently,the constructed photosensor achieves a high responsivity of 247.8 mA W^(-1)while simultaneously exhibiting excellent operating stability.Strikingly,based on the remarkable stability and high responsivity of the device,a glucose sensing system was established with a demonstration of glucose level determination in real human serum.This work offers a feasible and universal approach in the pursuit of high-performance bio-related sensing applications via a rational design of PEC devices in the form of nanostructured architecture with strategic doping engineering.

Structure and Wettability Engineering of Polycrystalline Diamond Films Treated by Thermally Oxidation,Second Growth and Surface Termination

High-quality polycrystalline diamond films with dominated(100)-oriented grains are realized by combining the thermally oxidation and the homogeneous second growth processes.Moreover,we investigate the wettability property of the polycrystalline diamonds in various stages.Different surface structures(with various grain sizes,voids,and orientations,etc.)and terminations(hydrogen or oxygen)have significant effects on the wettability of polycrystalline diamond films.The wettability is further closely related to the polarity of solutions.By measuring the contact angle and calculating the dispersion and polarity components,we estimate the surface energy of polycrystalline diamond films,and explore the factors affecting the surface energy.The modulations in growth quality and wettability property of polycrystalline diamond films provide valuable data for development of diamond-based multiple devices in practical applications.

Understanding of impact of carbon doping on background carrier conduction in GaN

The impact of carbon doping on the background carrier conduction in GaN has been investigated.It is found that the incorporation of carbon can effectively suppress the n-type background carrier concentration as expected.Moreover,from the fitting of the temperature-dependent carrier concentration and mobility,it is observed that high nitrogen-vacancy(VN)dominates the background carrier at room temperature which consequently results in n-type conduction.The doping agent(carbon atom)occupies the nitrogen site of GaN and forms CN deep acceptor as revealed from photoluminescence.Besides,a relatively low hole concentration is ionized at room temperature which was insufficient for the compensation of n-type background carriers.Therefore,we concluded that this background carrier concentration can be suppressed by carbon doping,which substitutes the N site of GaN and finally decreases the VN.

Normally-off AlGaN/GaN heterojunction field-effect transistors with in-situ AlN gate insulator

AlGaN/GaN heterojunction field-effect transistors(HFETs)with p-GaN cap layer are developed for normally-off operation,in which an in-situ grown AlN layer is utilized as the gate insulator.Compared with the SiNxgate insulator,the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region,which helps to positively shift the threshold voltage.In addition,the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown voltage.Owing to the introduction of AlN layer,normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is realized.Furthermore,the field-effect mobility is approximately 1500 cm^(2)·V^(-1)·s^(-1)in the 2DEG channel,implying a good device performance.

Hybrid-anode structure designed for a high-performance quasi-vertical GaN Schottky barrier diode

A quasi-vertical Ga N Schottky barrier diode with a hybrid anode structure is proposed to trade off the on-resistance and the breakdown voltage.By inserting a Si N dielectric between the anode metal with a relatively small length,it suppresses the electric field crowding effect without presenting an obvious effect on the forward characteristics.The enhanced breakdown voltage is ascribed to the charge-coupling effect between the insulation dielectric layer and Ga N.On the other hand,the current density is decreased beneath the dielectric layer with the increasing length of the Si N,resulting in a high on-resistance.Furthermore,the introduction of the field plate on the side wall forms an metal-oxide-semiconductor(MOS)channel and decreases the series resistance,but also shows an obvious electric field crowding effect at the bottom of the mesa due to the quasi-vertical structure.

GaN metal-oxide-semiconductor field-effect transistors on AIGaN/GaN heterostructure with recessed gate

GaN metal-oxide-semiconductor field-effect transistors （MOSFETs） on AIGaN/GaN heterostructure with a recess gate were fabricated and characterized. The device showed good pinch-off characteristics and a maximum field-effect mobility of 145.2 cm2.V-1.s-1. The effects of etching gas of CI2 and SiCI4 were investigated in the gate recess process. SiCI4-etched devices showed higher channel mobility and lower threshold voltage. Atomic force microscope measurement was done to investigate the etching profile with different etching protection mask. Compared with photoresist, SiO2- masked sample showed lower surface roughness and better profile with stepper sidewall and weaker trenching effect resulting in higher channel mobility in the MOSFET.