Surface Passivation Performance of Atomic-Layer-Deposited Al_2O_3 on p-type Silicon Substrates

Surface passivation performances of Al2O3 layers deposited on p-type Czochralski Si wafers by atomic layer deposition（ALD） were investigated as a function of post-deposition annealing conditions.The maximal minority carrier lifetime of 4.7 ms was obtained for AI2O3 passivated p-type Si.Surface passivation mechanisms of Al2O3 layers were investigated in terms of interfacial state density（Dit） and negative fixed charge densities（Qfix） through capacitance—voltage（C— V） characterization.High density of Qfix and low density of Dit were needed for high passivation performances,while high density of Dit and low density of Qfixdegraded the passivation performances.A low Dit was a prerequisite to benefit from the strong field effect passivation induced by high density of negative fixed charges in the Al2O3 layer.

Short-Term Synaptic Plasticity Mimicked on Ionic/Electronic Hybrid Oxide Synaptic Transistor Gated by Nanogranular SiO_2 Films

An indium-zinc-oxide （IZO） based ionic/electronic hybrid synaptic transistor gated by field-configurable nanogranular SiO2 films was reported. The devices exhibited a high current ON/OFF ratio of above 107, a high electron mobility of ～14 cm2 V^-1 s^-1 and a low subthreshold swing of ～80 mV/decade. The gate bias would modulate the interplay between protons and electrons at the channel/dielectric interface. Due to the dynamic modulation of the transient protons flux within the nanogranular SiO2 films, the channel current would be modified dynamically. Short-term synaptic plasticities, such as short-term potentiation and short- term depression, were mimicked on the proposed IZO synaptic transistor. The results indicate that the synaptic transistor proposed here has potential applications in future neuromorphic devices.

n-type Polycrystalhne Si Thick Films Deposited on SiN_x-coated Metallurgical Grade Si Substrates

For photovoltaic applications,low-cost SiNx-coated metallurgical grade silicon（MG-Si） wafers were used as substrates for polycrystalline silicon（poly-Si） thick films deposition at temperatures ranging from 640 to880 ℃ by thermal chemical vapor deposition.X-ray diffraction and Raman results indicated that high-quality poly-Si thick films were deposited at 880 ℃.To obtain n-type poly-Si,the as-deposited poly-Si films were annealed at 880 ℃ capped with a phosphosilicate glass.Electrical properties of the n-type poly-Si thick films were investigated by four-probe and Hall measurements.The carrier concentration and electron mobility of the n-type poly-Si film was estimated to be 1.7 x 1019cm-3and 68.1 cm2V-1s-1,respectively.Highquality poly-Si thick films deposited on MG-Si wafers are very promising for photovoltaic applications.