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Photoreflectance(PR) spectra of the graded InAlAs/InGaAs heterojunction bipolar transistor layers were investigated at various temperatures between 8 K and 300 K. The energy features of the PR spectra were fitted and identified as band‐to‐band transitions in the graded layers which were grown by pulsed molecular beam epitaxy (pulsed‐MBE) and InGaAs as well as InAlAs layers. The temperature variation of energy gaps can be described by the Varshni and Bose‐Einstein equations. A linear variation relationship of band gaps with Al composition (z) was observed and approximated to be E0(z)=0.809+0.769z eV at T=0 K. However, the parameters aB and ΘB derived from the Bose‐Einstein expression do not change meaningfully in the whole range of Al composition. From the observed Franz‐Keldysh oscillations (FKOs) we have evaluated the built‐in dc electric fields in the i‐InGaAs collector, i‐InGaAs spacer and n‐InAlAs emitter regions. The electric fields are in good agreement with the continuity condition of electric disp...

In this study of resistance random access memory in a resistive switching film, the breakdown degree was controlled by varying forming current compliance. A SiOx layer was introduced into the ZnO layer of the structure to induce both typical bipolar resistive switching (RS) and complementary resistive switching (CRS). In addition, the SiOx layer-generated vacuum spaces in typical bipolar RS can be verified by electrical characteristics. Changing forming current compliance strikingly modifies the oxygen storage capacity of the inserted SiOx layer. CRS can be achieved, therefore, by tuning the oxygen ion storage behavior made possible by the SiOx layer.

The photoreflectance (PR) spectroscopic technique has been used to investigate the microstructures of the graded InAlAs/InGaAs heterojunction bipolar transistor at room temperature. The energy features of the PR spectrum were fitted and identified as band‐to‐band transitions in the graded layers which were grown using pulsed molecular beam epitaxy and InGaAs as well as InAlAs layers. A linear variation relationship of band gaps with Al composition z was observed and approximated by Eg=0.737+0.759z eV. From the observed Franz‐Keldysh oscillations, we have evaluated the built‐in dc electric fields in the i‐InGaAs collector and n‐InAlAs emitter regions. These electric fields are in good agreement with the continuity condition of electric displacements in the interfaces.

We have measured the photoreflectance spectrum at 300 K from a lattice‐matched InAlAs/InGaAs heterostructure bipolar transistor grown by molecular beam epitaxy. The energy features of photoreflectance spectra have been identified and the built‐in dc electric fields and associated doping profiles have been evaluated in the n‐InAlAs emitter from the observed Franz–Keldysh oscillations. The undoped InGaAs spacer between emitter and base was added on to change the built‐in electric field. The results showed that the energy features above the InGaAs band gap are the transitions from the valence band to the quantized state of the conduction band. The quantum well of the conduction band is in the interface of the InAlAs and InGaAs heterojunction. The interface charge densities in the spacer channel are determined to be 3.54×1011 cm−2 and 4.22×1011 cm−2, corresponding to the samples with spacer thicknesses of 300 and 500 A, respectively. A triangular potential profile model was used to calculate the microstructur...

This study presents the dual bipolar resistive switching characteristics induced by oxygen-ion accumulation. By introducing nitrogen to the interface between the resistive switching region and active switching electrode, filament-type and interface-type resistive switching behaviors can both exist under different operation conditions. This particular oxygen-ion accumulation-induced switching behavior suggests an extraordinary potential for resistive random access memory applications because the operating power can be significantly decreased (about 100 times). The physical mechanism of this oxygen-ion accumulation-induced interface-type resistive switching behavior is explained by our model and clarified by current conduction mechanism and material analysis.

A low-temperature ultra-violet (UV) light enhanced supercritical CO2 (SCCO2) fluid treatment is employed to improve the performance of In-Ga-Zn-O (IGZO) thin film transistor (TFT) device. In this study, amorphous IGZO film deposited by sputtering is investigated in SCCO2 ambient under different illumination conditions. After SCCO2 treatment with UV exposure, the mobility and subthreshold swing of the TFT can be significantly improved. A model is proposed to explain the mechanism, and the improvement is due to the reduction of dangling bonds at the grain boundary. With the help of UV, dangling bonds can be effectively passivated by OH chemical groups.

In this paper, multi-layer Zn:SiO2/SiO2 structure is introduced to reduce the operation power consumption of resistive random access memory (RRAM) device by modifying the filament formation process. And the configuration of multi-layer Zn:SiO2/SiO2 structure is confirmed and demonstrated by auger electron spectrum. Material analysis together with conduction current fitting is applied to qualitatively evaluate the carrier conduction mechanism on both low resistance state and high resistance state. Finally, single layer and multilayer conduction models are proposed, respectively, to clarify the corresponding conduction characteristics of two types of RRAM devices.

In this Letter, the characteristics of set process of hafnium oxide based resistance random access memory are investigated by different set processes with increasing compliance current. Through current fitting, carrier conduction mechanism of low resistance state changes from hopping to surface scattering and finally to ohmic conduction with the increase of setting compliance current. Experimental data of current-voltage measurement under successive increasing temperature confirms the conduction mechanism transition. A model of filament growth is eventually proposed in a way by merging discrete metal precipitates and electrical field simulation by comsol Multiphysics further clarifies the properties of filament growth process.

In this study, the electrical conduction mechanism of Zn:SiOx resistance random access memory (RRAM) treated with supercritical CO2 fluid (SCCO2) process was investigated by low temperature measurement. The current of low resistance state for current-voltage curves in SCCO2-treated and untreated Zn:SiOx RRAM were measured and compared under a low temperature range from 100 K to 298 K. The electrical conduction mechanisms of hopping conduction and metal-like behaviors in SCCO2-treated and untreated Zn:SiOx RRAM were discussed, respectively. Finally, the electrical conduction mechanism was analyzed and verified by the chemical composition and bonding intensity of XPS analyses.

In this study, the hopping conduction distance variation of Zn:SiO2 resistance random access memory (RRAM) devices with different operating compliance currents was discussed and verified. To investigate and determine the hopping conduction distance dependent activation energy characteristics, the Arrhenius plot of low resistance state of Zn:SiO2 RRAM devices was applied, from which we proposed carrier conduction model. With the increase of current compliance, more metal ions would accumulate to form precipitates with larger diameter, which in turn resulted in the shortening of hopping distance. Because of shorter hopping distance, activation energy for carrier hopping would decrease.