Electrophysical Characteristics of the Pentacene-based MIS Structures with a SiO2 Insulator

Russian Physics Journal - In a wide range of frequencies and temperatures, the admittance of MIS structures based on pentacene organic films, formed by thermal evaporation in vacuum on SiO2 and...     

Photoelectrical characteristics of MIS structures on the basis of graded-band-gap n-HgCdTe (x = 0.21–0.23)

Voltage, frequency, and temperature dependences of photo-emf are experimentally studied in the MIS HgCdTe/SiO ₂ /Si ₃ N ₄ and HgCdTe/AOF structures. The MIS structures were produced on the basis of graded-bandgap Hg _1−x Cd _x Te films grown by molecular-beam epitaxy on GaAs substrates. It is found that the subsurface graded-band-gap layers do affect the photoelectrical characteristics of MIS structures. The mechanisms limiting the differential resistance in the space-charge region at various temperatures are revealed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 70–80, October, 2006.     

The Influence of Resistance of the Epitaxial-Film Volume on the Capacity-Voltage Characteristics of the HgCdTe/AOF and HgCdTe/SiO<Subscript>2</Subscript>/Si<Subscript>3</Subscript>N<Subscript>4</Subscript> MIS Structures

The dependence of active and reactive components of the admittance of MIS structures based on heteroepitaxial Hg_0.78Cd_0.22Te produced by molecular-beam epitaxy as a function of bias voltage is experimentally studied in the frequency range 1 kHz − 1 MHz. The resistance of the epitaxial-film volume is shown to significantly affect the measured admittance in the case where the electron concentration in HgCdTe is up to 5·10¹⁴ cm^{− 3}, and this is manifested in a number of features of the capacity-voltage characteristics. The resistance of the epitaxial-film volume is found for the samples with different initial conductivity and for the samples with graded-band subsurface layers. The techniques are proposed that make it possible to avoid the influence of volume resistance on the admittance of MIS structures on the basis of heteroepitaxial HgCdTe. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 31–37, June, 2005.     

光伏型碲镉汞红外探测单元响应特性分析

对激光辐照PV型的Hg1-xCdxTe单元探测器的响应特性进行了研究,建立了材料内部光生电动势变化的数学分析模型。计算了不同光源辐照3类组分不同的Hg1-xCdxTe探测单元的输出特性,并对温度波动影响进行了分析。结果表明:在光敏面积恒定时,x值越大探测器的完全饱和电压越大,即探测器的响应度Hg0.627Cd0.373TeHg0.698Cd0.302TeHg0.819Cd0.181Te;x值越小,探测器受温度波动的影响越小。     

Special Features of Local Photoelectrical Properties of Inhomogeneous Metal–Insulator–Semiconductor Structures

Local photoelectrical measurements are used to study anomalous electrical properties of metal–insulator–semiconductor structures (decrease in photoemf in inversion). The inhomogeneous surface potential in the gap between the regions beneath and behind the electrode and between different parts of the region beneath the electrode may lead to a decrease in the local photoemf in inversion.     

Cluster Model of the Mechanism of Sensitivity of Gas Sensors Based on MIS Structures

A cluster model of the mechanism of sensitivity to gases is proposed, according to which the change in the electric capacity of a MIS sensor under the action of gas is caused by a change in the dielectric constant of the metal — dielectric transition layer under the action of gas molecules. The dielectric constant of the transition layer changes due to the rearrangement of the electronic structure of the traps.

     

Impedance of MIS Devices Based on nBn Structures from Mercury Cadmium Telluride

Russian Physics Journal - Three types of nBn structures based on mercury cadmium telluride grown by molecular beam epitaxy have been fabricated. As barrier layers in nBn structures,...     

基于反射光谱特性的土壤分类研究

选取中国松嫩平原吉林省农安县主要土壤(黑土、黑钙土、草甸土、风砂土、冲积土)室内光谱反射率作为研究对象,利用去包络线方法提取反射光谱特征指标,作为输入变量建立BP神经网络模型,进行土壤分类研究,探索利用表层土壤反射光谱特性进行土壤分类的可行性。结果表明:(1)包络线去除后的曲线使土壤可见光近红外波段的吸收特征显著增强;农安县不同土壤在400～2500nm范围内主要有5个光谱吸收谷,前2个吸收谷主要是由于土壤有机质、铁及土壤机械组成引起的,后3个是土壤水分吸收光谱能量引起的;不同土壤类型反射光谱的差异主要表现在前2个吸收谷。(2)由于输入变量的选取客观准确,基于前2个吸收谷形状特征的BP神经网络模型的土壤分类精度显著优于以反射率或5个吸收谷形状特征为输入变量的模型,可以用于土壤分类。     

Electrophysical characteristics of MIS structures based on graded band-gap MBE HgCdTe with grown in situ CdTe as a dielectric

Capacitance-voltage characteristics of MIS structures based on graded band-gap heteroepitaxial HgCdTe (x = 0.22–0.23 and 0.32–0.36) with grown in situ CdTe as a passivating coating are examined. The average surface-state densities as well as mobile- and fixed-charge densities are determined for the HgCdTe/CdTe, HgCdTe/CdTe–SiO₂–Si₃N₄, and HgCdTe/CdTe–ZnTe systems. It is shown that grown in situ CdTe forms a fairly qualitative interface, and deposition of additional SiO₂–Si₃N₄ and ZnTe layers makes it possible to control the electric strength and charges in the dielectric used.     

Investigation into MIS structures based on gradedband-gap hetero-epitaxial HgCdTe grown by molecular-beam epitaxy using photo-emf and conductivity methods

The effect of graded-band-gap layers on the differential resistance of space-charge region in MIS structures based on MBE HgCdTe (x = 0.225) is examined. It is shown that the effect of resistance of the epitaxial-film bulk on the measured capacitance and resistance should be taken into account for correct determination of space-charge region parameters. The presence of near-surface layers with increased Cd contents results in an increase in the resistance of the space-charge region in strong inversion. The product of semiconductor resistance by area as high as 15 Ω⋅cm² is obtained despite suppression of tunnel generation-recombination through deep levels in MIS structures with graded-band-gap layers. This might be due to background photogeneration and diffusion of minority charge carriers. The mechanisms for limitation of the differential resistance of space-charge region at different temperatures are discussed for n-HgCdTe (x = 0.225 and 0.292) and p-HgCdTe (x = 0.225).     

Switching Channel Development Dynamics in Planar Structures on the Basis of Vanadium Dioxide

The results of the experimental studies and numerical simulation of the switching channel development dynamics in planar structures on the basis of vanadium dioxide are reported. The obtained data on the variation of the temperature in the channel with time and of the current arisen after the pulsed load, and on the times of transition from the high-resistance to the low-resistance state and back are analyzed in order to determine the switching mechanism and to predict the functional characteristics of the switchable vanadium- oxide structures as promising materials for the creation of relaxation generators that can serve as prototypes of neural oscillators. It is shown that the switching behavior is associated with the metal–semiconductor phase transition in vanadium dioxide, which is stimulated by the emission of Joule heat.     

GaN基MIS紫外探测器的电学及光电特性

制备了GaN基金属-绝缘层-半导体(MIS)结构紫外探测器,并测量了其暗电流和光谱响应。通过分析其暗电流,发现在反偏情况下,其主要电流输运机制为隧穿复合机制;在正偏情况下,随着偏压的增大,电流输运机制从隧穿机制变为空间电荷限制电流机制。光谱响应测试结果显示,该探测器在-5 V的偏压下,在315 nm处获得了最大响应度170 mA/W,探测度为2.3×10¹² cm·Hz^1/2·W^-1。此外,还研究了不同厚度I层对器件光电压的影响,结果表明,光电压受隧穿机制与漏电流机制的共同制约。     

Modeling of IR Spectra of Compounds on the Basis of Analogy between Fragmental Compositions of Structures

The possibility of using representations of the structures of compounds in the form of nonisomorphic k-vertex connective fragments for modeling IR spectra of compounds with a given structure on the basis of the spectra of their close structural analogs selected from a database is shown. Statistical justification of the approach and examples of modeled spectra are given.     

Topological insulators based on the semi-metallic HgCdTe

The review of peculiarity of growth and experimental results of the magneto-transport measurements (longitudinal magneto-resistance R_xx and the Hall resistance R_xy) over a wide interval of temperatures for several samples of Hg_1?xCd_xTe (x ≈ 0.13–0.15) grown by MBE is presented in this paper. An amazing temperature stability of the SdH-oscillation period and amplitude is observed in the entire temperature interval of measurements up to 50 K. Moreover, the quantum Hall effect (QHE) behaviour of the Hall resistance was shown in the same temperature interval. These peculiarities of the R_xx and R_xy for strained thin layers are interpreted using quantum Hall conductivity (QHC) on topologically protected surface states (TPSS). In the case of not strained layers it is assumed that the QHC on the TPSS contributes also to the conductance of the bulk samples. The experimental results on magneto-transport (QHC and SdH) obtained for the strained 100 nm thickness Hg_1?xCd_xTe layer are interpreted on the basis of the 8 × 8 kp model and an advantage of the Hg_1?xCd_xTe as topological insulators is shown. This article is an expanded version of the scientific reports presented at the International Conference on Semiconductor Nanostructures for Optoelectronics and Biosensors 2016 ICSeNOB2016, May 22–25, 2016, Rzeszow, Poland.     

Influence of Carbon Multiple Treatments on the Photoelectrical Properties of Porous Glasses

We have studied the influence of multiple carbon treatments on the properties of silica porous glasses. Each step of each carbon treatment started with filling the voids of porous glass with carbon. During the following anneal carbon interacted with the walls of the voids. It was shown that low dimensional silicon clusters were formed inside the voids as a result of this reaction. In the experiments the photoluminescence spectra and conductivity of carbon-processed specimens were measured. The size-distribution of voids in porous glasses was calculated from absorption—desorption isotherms. An original technique was proposed that allowed to obtain the size-distribution of silicon clusters from the positions of peaks in the photoluminescence spectra. Correlation between the photoluminescence intensity and the sizes of pores was revealed. The observed oscillations in the shapes of the photoluminescence spectra in subsequent cycles of carbon treatment are explained by changes of the number of clusters corresponding to definite peaks in the size distribution spectra.     

Charge Effects in the Dielectric Films of MIS Structures under the Concurrent Influence of Radiation and High-Field Electron Injection

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - Based on the obtained experimental data, a model is developed for the processes of a variation in the charge state of...     

周期性轴对称凹槽结构隔声特性数值模拟

提出一种在钻铤上切割周期性轴对称凹槽方式构建隔声体,消除钻铤模式波的方法.结果表明,其隔声效果与凹槽深度H、长度L、凹槽数目N、凹槽截面形状以及钻铤壁厚有关.选择矩形截面凹槽、减小钻铤壁厚、增加凹槽深度都可有效提高隔声体的隔声效果,该结构最高可获得约36 dB的声衰减,基本满足随钻声波测井仪器对隔声效果要求.