Impact of Al_(x)Ga_(1-x)N barrier thickness and Al composition on electrical properties of ferroelectric HfZrO/Al_(2)O_(3)/AlGaN/GaN MFSHEMTs

Ferroelectric(FE)HfZrO/Al_(2)O_(3) gate stack AlGaN/GaN metal-FE-semiconductor heterostructure high-electron mo-bility transistors(MFSHEMTs)with varying Al_(x)Ga_(1-x)N barrier thickness and Al composition are investigated and com-pared by TCAD simulation with non-FE HfO_(2)/Al_(2)O_(3) gate stack metal-insulator-semiconductor heterostructure high-electron mobility transistors(MISHEMTs).Results show that the decrease of the two-dimensional electron gas(2DEG)density with decreasing AlGaN barrier thickness is more effectively suppressed in MFSHEMTs than that in MISHEMTs due to the enhanced FE polarization switching efficiency.The electrical characteristics of MFSHEMTs,including transcon-ductance,subthreshold swing,and on-state current,effectively improve with decreasing AlGaN thickness in MFSHEMTs.High Al composition in AlGaN barrier layers that are under 3-nm thickness plays a great role in enhancing the 2DEG den-sity and FE polarization in MFSHEMTs,improving the transconductance and the on-state current.The subthreshold swing and threshold voltage can be reduced by decreasing the AlGaN thickness and Al composition in MFSHEMTs,affording favorable conditions for further enhancing the device.

Structure and luminescence of α-plane GaN on γ-plane sapphire substrate modified by Si implantation

We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation.Upon gradually raising Si fluences from 5×10^(13)cm^(-2)to 5×10^(15)cm^(-2),the n-type dopant concentration gradually increases from 4.6×10^(18)cm^(-2)to 4.5×10^(20)cm^(-2),while the generated vacancy density accordingly raises from 3.7×10^(13)cm^(-2)to 3.8×10^(15)cm^(-2).Moreover,despite that the implantation enhances structural disorder,the epitaxial structure of the implanted region is still well preserved which is confirmed by Rutherford backscattering channeling spectrometry measurements.The monotonical uniaxial lattice expansion along the a direction(out-of-plane direction)is observed as a function of fluences till 1×10^(15)cm^(-2),which ceases at the overdose of 5×10^(15)cm^(-2)due to the partial amorphization in the surface region.Upon raising irradiation dose,a yellow emission in the as-grown sample is gradually quenched,probably due to the irradiation-induced generation of non-radiative recombination centers.

Organic-2D composite material-based RRAM with high reliability for mimicking synaptic behavior

The field of artificial intelligence and neural computing has been rapidly expanding due to the imple-mentation of resistive random-access memory(RRAM)based artificial synaptic.However,the low flexibility of conventional RRAM materials hinders their ability to mimic synaptic behavior accurately.To overcome such limitation,organic-2D composites with high mechanical properties are proposed as the active layer of RRAM.Moreover,we enhance the reliability of the device by ZrO_(2)insertion layer,resulting in stable synaptic performance.The Ag/PVA:h-BN/ZrO_(2)/ITO devices show stable bipolar resistive switching behavior with an ON/OFF ratio of over 5×10^(2),a~2400 cycles endurance and a long retention time(>6×10^(3)s),which are essential for the development of high-performance RRAMs.We also study the possible synaptic mechanism and dynamic plasticity of the memory device,observing the transition from short-term potentiation(STP)to long-term potentiation(LTP)under the effect of continuous voltage pulses.Moreover,the device exhibits both long-term depression(LTD)and paired-pulse facili-tation(PPF)properties,which have significant implications for the design of organic-2D composite material RRAMs that aim to mimic biological synapses,representing promising avenues for the devel-opment of advanced neuromorphic computing systems.

Band-gap tunable(Ga_(x)In_(1−x))_(2)O_(3)layer grown by magnetron sputtering

Multicomponent oxide(Ga_(x)In_(1−x))_(2)O_(3)films are prepared on(0001)sapphire substrates to realize a tunable band-gap by magnetron sputtering technology followed by thermal annealing.The optical properties and band structure evolution over the whole range of compositions in ternary compounds(Ga_(x)In_(1−x))_(2)O_(3)are investigated in detail.The X-ray diffraction spectra clearly indicate that(Ga_(x)In_(1−x))_(2)O_(3)films with Ga content varying from 0.11 to 0.55 have both cubic and monoclinic structures,and that for films with Ga content higher than 0.74,only the monoclinic structure appears.The transmittance of all films is greater than 86%in the visible range with sharp absorption edges and clear fringes.In addition,a blue shift of ultraviolet absorption edges from 380 to 250 nm is noted with increasing Ga content,indicating increasing band-gap energy from 3.61 to 4.64 eV.The experimental results lay a foundation for the application of transparent conductive compound(Ga_(x)In_(1−x))_(2)O_(3)thin films in photoelectric and photovoltaic industry,especially in display,light-emitting diode,and solar cell applications.