Using an identical monolithic InGaN/GaN light emitting diode (LED) array as the sensing module and a well-designed data processing module, we demonstrate a small-size concentration sensing prototype. Overlap between the emission and the response spectra of the InGaN/GaN LED makes each pair of LEDs in the arrayed chip form a sensing channel. The changes in liquid concentration can be transformed into variation of photocurrent. The system's sensing properties are further optimized by varying the position, number of receivers, and packaging reflectors. With methyl orange as a tracer agent, the sensing system's resolution is 0.286 μmol/L with a linear measurement region below 40 μmol/L.
The InGaN films and GaN/InGaN/GaN tunnel junctions(TJs)were grown on GaN templates with plasma-assisted molecular beam epitaxy.As the In content increases,the quality of InGaN films grown on GaN templates decreases and the surface roughness of the samples increases.V-pits and trench defects were not found in the AFM images.p++-GaN/InGaN/n++-GaN TJs were investigated for various In content,InGaN thicknesses and doping concentration in the InGaN insert layer.The InGaN insert layer can promote good interband tunneling in GaN/InGaN/GaN TJ and significantly reduce operating voltage when doping is sufficiently high.The current density increases with increasing In content for the 3 nm InGaN insert layer,which is achieved by reducing the depletion zone width and the height of the potential barrier.At a forward current density of 500 A/cm^(2),the measured voltage was 4.31 V and the differential resistance was measured to be 3.75×10^(−3)Ω·cm^(2)for the device with a 3 nm p++-In_(0.35)Ga_(0.65)N insert layer.When the thickness of the In_(0.35)Ga_(0.65)N layer is closer to the“balanced”thickness,the TJ current density is higher.If the thickness is too high or too low,the width of the depletion zone will increase and the current density will decrease.The undoped InGaN layer has a better performance than n-type doping in the TJ.Polarization-engineered tunnel junctions can enhance the functionality and performance of electronic and optoelectronic devices.
Jun FangFan ZhangWenxian YangAiqin TianJianping LiuShulong LuHui Yang
To improve the internal quantum efficiency(IQE)and light output power of In Ga N light-emitting diodes(LEDs),we proposed an In-composition gradient increase and decrease In Ga N quantum barrier structure.Through analysis of its P-I graph,carrier concentration,and energy band diagram,the results showed that when the current was 100 m A,the In-composition gradient decrease quantum barrier(QB)structure could effectively suppress electron leakage while improving hole injection efficiency,resulting in an increase in carrier concentration in the active region and an improvement in the effective recombination rate in the quantum well(QW).As a result,the IQE and output power of the LED were effectively improved.
SANG XienXU YuanYIN MengshuangWANG FangLIOU Juin JLIU Yuhuai
Light-driven dry reforming of methane toward syngas presents a proper solution for alleviating climate change and for the sustainable supply of transportation fuels and chemicals.Herein,Rh/InGaN_(1-x)O_(x) nanowires supported by silicon wafer are explored as an ideal platform for loading Rh nanoparticles,thus assembling a new nanoarchitecture for this grand topic.In combination with the remarkable photothermal synergy,the O atoms in Rh/InGaN_(1-x)O_(x) can significantly lower the apparent activation energy of dry reforming of methane from 2.96 eV downward to 1.70 eV.The as-designed Rh/InGaN_(1-x)O_(x) NWs nanoarchitecture thus demonstrates a measurable syngas evolution rate of 180.9 mmol g_(cat)^(-1) h^(-1) with a marked selectivity of 96.3% under concentrated light illumination of 6 W cm^(-2).What is more,a high turnover number(TON)of 4182 mol syngas per mole Rh has been realized after six reuse cycles without obvious activity degradation.The correlative 18O isotope labeling experiments,in-situ irradiated X-ray photoelectron spectroscopy(ISI-XPS)and in-situ diffuse reflectance Fourier transform infrared spectroscopy characterizations,as well as density functional theory calculations reveal that under light illumination,Rh/InGaN_(1-x)O_(x) NWs facilitate releasing^(*)CH_(3) and H^(+)from CH_(4) by holes,followed by H_(2) evolution from H^(+)reduction with electrons.Subsequently,the O atoms in Rh/InGaN_(1-x)O_(x) can directly participate in CO generation by reacting with the ^(*)C species from CH_(4) dehydrogenation and contributes to the coke elimination,in concurrent formation of O vacancies.The resultant O vacancies are then replenished by CO_(2),showing an ideal chemical loop.This work presents a green strategy for syngas production via light-driven dry reforming of methane.
