Application of the transverse acoustoelectric effect to studying silicon surface charging upon water adsorption

Water adsorption on a silicon surface in a layered Si-LiNbO₃ structure with an air gap is studied using the transverse acoustoelectric effect on surface acoustic waves. A generalized analysis of measurements of the transverse acoustoelectric effect makes it possible to determine the initial band bending of the Si surface, its changes during gas cycles, hence, the sign and charging kinetics of Si upon H₂O adsorption. Depending on the properties of the semiconductor surface defects, both the donor and acceptor nature of the interaction of H₂O with Si are observed. For samples with a thermal oxide, the donor-type interaction occurs; for samples with a natural oxide, both interaction types take place. Based on the used physical model of oxide charging upon exposure to an adsorbate, a comprehensive methodical approach is proposed, which allows the targeted development of acoustoelectronic structures for sensor applications.     

Formation of schottky barriers on GaAs(110): from adsorbate-lnduced gap states to interface metallicity

The formation of Ga-, Mn- and Ca-GaAs(110) interfaces is studied with soft x-ray and ultra-violet photoemission spectroscopy. Band bending at the semiconductor surface is analyzed in terms of a two-step model of the pinning of the Fermi level. At low coverage, adsorbate induced donor states produce rapid band bending on p-GaAs. A well defined trend in the energy level of the adsorbate-induced donor state vs ionization energy of the adatom emerges from these and previous data on In-, A1-, Ag-, Au-, Pd-, and Sn-GaAs(110) interfaces. At high coverage, the pinning of the Fermi level is associated with appearance of metallic character at the interface.     

Nonlinear interaction of acoustic surface waves in epitaxial gallium arsenide

A technique is described for obtaining the nonlinear interaction between two surface waves propagating in a piezoelectric semiconductor. The coupling between the waves is associated with the transverse electric fields of the surface wave and the carriers in the semiconductor. The effective carrier concentration for the interaction has been altered by forming a surface-depletion region beneath a metal?semiconductor contact. This scheme has been used to produce the convolution of two oppositely travelling acoustic waves in epitaxial gallium arsenide, and it has been found that a strong nonlinearity can be obtained at small acoustic-power levels.     

紫外激光与半导体相互作用研究进展综述

紫外激光与半导体相互作用是当今国内外研究的热点。综述了紫外激光与半导体相互作用在光电子产业、激光加工、激光表面改性等方面的应用。介绍了紫外激光与半导体相互作用的基本原理,总结了紫外激光烧蚀半导体的理论模型,包括热传导模型、载流子耦合扩散模型、光化学模型、表面热蒸发模型、双温模型、表面充电模型等。总结了关于损伤形貌、烧蚀阈值和紫外激光损伤半导体机理的实验研究。提出了紫外激光与半导体相互作用可能的研究和新的应用方向。     

CdTe半导体中弱耦合表面磁极化子的有效质量

本文研究了ＣｄＴｅ半导体中电子与我学（ＳＯ）声子及体纵光学（ＬＯ）声子一经耦合的表面磁极化子的性质。采用改进的线性组合逄符和微扰法计算了半导体中表面磁极化子的有效哈密顿量;当计及电子在反剖效应中,发射和吸收不同波矢的声子之间相互作用时,讨论其对ＣｄＴｅ半导体中弱耦合表面磁极化子有效质量的影响。     

极性半导体中经由形变势的表面磁极化子的性质

采用改进了的线性组合算符和微扰法,研究极性半导体中电子与表面光学声子耦合强,与表面声学声子耦合弱的表面磁极化子的性质。讨论了电子在反冲效应中发射和吸收不同波矢的声子之间相互作用对极性半导体中经由表变势的表面磁极化子的有效哈密顿量,频率,诱生势和有效质量的影响。     

A normal mode theory for the Rayleigh wave amplifier

A Rayleigh acoustic wave traveling on the surface of a semi-infinite piezoelectric medium may be amplified by interaction with drifting carriers in an adjacent semiconductor. The gain and frequency response of this interaction is determined here by using a normal mode expansion of the Rayleigh wave piezoelectric fields. The configuration which uses a thin semiconductor film supported by a semi-infinite dielectric and separated from the piezoelectric by a small air gap is described in detail and the results are expressed in a form that clearly shows the effect of piezoelectric, air gap, and semiconductor parameters. Comparisons with experimental data for the lithium niobate-silicon film configuration show that acoustic gains on the order of 100 dB/cm can be obtained in the frequency range above 0.1 GHz.     

CdF_2半导体膜中电子-表面声子强耦合对极化子性质的影响

采用改进的 Huybrechts线性组合算符和变分方法 ,研究了半导体膜内电子与表面光学声子强耦合、与体纵光学声子弱耦合对极化子性质的影响 ,得到了极化子的有效质量和自陷能随膜厚的变化规律 .对 Cd F2 半导体 ,计算了不同支声子与电子的相互作用对极化子有效质量和自陷能的贡献     

基于太赫兹等离激元的半导体表面生化薄膜光谱检测

我们提出了一种利用太赫兹表面等离激元对放置在半导体表面的生化薄膜进行光谱测量的新方法。我们从理论上证明了半导体材料对其上传输的太赫兹表面等离子体波具有较强的表面束缚性,从而提高太赫兹波与半导体表面的生化薄膜之间的相互作用。通过采用太赫兹时域光谱测量系统,我们从实验上分别得到了洋葱表皮的太赫兹表面等离子体波和自由空间太赫兹波透射波谱。实验结果表明,当测量对象是厚度仅为自由空间太赫兹波波长的约百分之一的单层洋葱表皮时,表面等离子体波的透射波谱与自由空间太赫兹波透射波谱相比具有更加多的特征吸收峰。     

Static characteristics of the metal-insulator-semiconductor- insulator-metal (MISIM) structure—II. Low frequency capacitance

It is shown that the reciprocal value of low frequency capacitance of a MISIM structure can be represented by a sum of reciprocal values of insulator layer and surface space charge capacitances and an “interaction” term which is a consequence of the finiteness of the semiconductor layer. General formulae are derived for the low frequency capacitance of a MISIM structure with nondegenerate semiconductor. Analytical and numerical calculations are given for a MISIM structure with intrinsic semiconductor layer.     

Semiconductor surface study by transverse acoustoelectric voltage using surface acoustic waves

Electrical properties of semiconductor surfaces can be determined by measuring the transverse acoustoelectric voltage. This voltage is produced by the interaction of the surface acoustic wave propagating on a piezoelectric substrate and the carriers on semiconductor surface placed in proximity. Using 110 MHz LiNbO₃ delay lines, the transverse acoustoelectric voltage has been measured across CdS and Si, the surface properties of which are varied by different light illumination. Detailed study of the voltage waveform reveals the type of traps and the amount of charge in the traps. The method is simple, needs no contacts to the sample, and is sensitive.     

GaSb半导体表面极化子基态能量的研究

采用Ｌ．Ｌ．Ｐ方法导出表面极化子的基态能量,声子平均数,讨论了电子在反冲效应中发射和吸收不同波矢声子之间相互作用对ＧａＳｂ半导体表面中表面极化子基态能量的影响。数值计算结果表明：当动量趋于零时,声子之间的相互作用对极化子性质无影响;当动量达到某一值时,声子之间相互作用的能量占极化子总能量中非常显著的部分;随着动量（平方）的增加,声子平均数近似线性地增加。     

Study of the surface properties of thermally oxidized silicon using surface acoustic wave attenuation

In the separate media space charged coupled convolver, the interaction of a surface acoustic wave (SAW) with the free carriers in an adjacent semiconductor results in attenuation of the acoustic wave. The magnitude of the attenuation is dependent on the concentration of the free carriers near the surface. An externally applied d.c. voltage changes the surface carrier concentration and this change is reflected in SAW attenuation. Analysis of the SAW attenuation caused by a continuous d.c. field gives an estimate of the surface state density. The time required for the SAW attenuation to reach steady state after the semiconductor is driven into deep depletion is an indication of the rate of carrier generation in the depletion region. Transient effects have also been observed using a synchronously applied d.c. pulse.     

Density functional theory study of first-layer adsorption of ZrO2 and HfO2 on Ge(1 0 0)

Density functional theory was used to performed a survey of transition metal oxide (MO₂ = ZrO₂, HfO₂) ordered molecular adsorbate bonding configurations on the Ge(1 0 0)-4 × 2 surface. Surface binding geometries of metal-down (O-M-Ge) and oxygen-down (M-O-Ge) were considered, including both adsorbate and displacement geometries of M-O-Ge. Calculated enthalpies of adsorption show that bonding geometries with metal-Ge bonds (O-M-Ge) are essentially degenerate with oxygen-Ge bonding (M-O-Ge). Calculated electronic structures indicate that adsorbate surface bonding geometries of the form O-M-Ge tend to create a metallic interfaces, while M-O-Ge geometries produce, in general, much more favorable electronic structures. Hydrogen passivation of both oxygen and metal dangling bonds was found to improve the electronic structure of both types of MO₂ adsorbate systems, and induced the opening of true semiconducting band gaps for the adsorbate-type M-O-Ge geometries. Shifts observed in the DOS minima for both O-M-Ge and M-O-Ge adsorbate geometries are consistent with surface band bending induced by the adsorbate films, where such band bending extends much further into the Ge substrate than can be modeled by the Ge slabs used in this work.     

Kinetics of the interaction between a CCl<Subscript>2</Subscript>F<Subscript>2</Subscript> radio-frequency discharge and gallium arsenide

Halogen-containing plasma, particularly, freons, is often used to form topologies on the surface of semiconductors. This paper investigates the kinetics of the interaction between the R-12 freon and the surface of a semiconductor structure. The R-12 freon is effective for etching semiconductors, particularly, gallium arsenide, as it provides sufficient rates of interaction while preserving a uniform and clean surface. In this work, the surface of the samples is inspected with a Solver P47Pro atomic-force microscope.     

Tuning Photoelectrochemical and Photocatalytic Properties through Electronic Semiconductor–Support Interaction

Do semiconductor–support interactions influence the bandgap energy? For cadmium sulfide supported onto silica it is shown that the bandgap increases with decreasing coverage. The photocatalytic activity of these heterogeneous photocatalysts increases in the same way as illustrated by the relative rate of an addition reaction. Based on experimental data it is concluded that these changes originate from an electronic semiconductor–support interaction (SEMSI) mediated through surface [Si]–O–CdS bonds. It is seen that the effect also changes the flatband potential and charge carrier lifetimes.     

Reversible Degradation of Ohmic Contacts on p-GaN for Application in High-Brightness LEDs

This paper analyzes the high-temperature long-term stability of ohmic contacts on p-type gallium nitride (p-GaN). The contributions of the ohmic contacts and semiconductor material degradation are separated by adopting the transmission line method (TLM). Before stress, the current-voltage (I-V) curves measured at the pads of the TLMs showed a linear shape, indicating a good ohmic behavior of the contacts. Thermal treatment at 250degC was found to induce the worsening of the electrical characteristics of the contacts: identified degradation modes consist of a shift of the I-V curves toward higher voltages and strong nonlinearity of the characteristics around zero. This paper shows that the high-temperature instabilities of ohmic contacts on p-GaN are related to the interaction between the device surface and the plasma-enhanced chemical vapor deposition SiN passivation layer. Hydrogen contained in the passivation layer is supposed to play an important role in the degradation process: the interaction with the acceptor dopant at the metal/semiconductor interface induces the decrease of the effective acceptor concentration. As a consequence, both the ohmic contact characteristics and the semiconductor sheet resistance are worsened.     

Effect of surface on the excitonic characteristics of semiconductors

The effect of surface treatments on the main characteristics of excitons in the subsurface region of semiconductors (for GaAs), as well as the spatial distribution of main characteristics of excitons (for CdS), was studied. An analysis of experimental data showed that the deposition of insulator layers with a lower dielectric constant on the surface of the semiconductor resulted in an enhancement of the exciton-phonon interaction and an increase in the exciton binding energy. The appearance of the surface layer with a higher defect concentration increasing after some surface treatments results in the lowering of the exciton binding energy in the subsurface region and also in the weakening of the exciton-phonon interaction.     

飞秒激光作用下薄膜的热力学研究

为了描述飞秒激光与金属薄膜相互作用过程中的非平衡传热现象,采用有限差分的方法对金属薄膜内的温度场进行了1维数值模拟。对双温模型中电子-晶格耦合系数G、激光脉宽和电子的弹道运动等因素对金属薄膜表层电子和晶格温度的影响进行了理论分析。结果表明,G影响材料表面电子的温升,电子和晶格温度平衡时的延迟时间随着G的增大而减小,二者呈指数变化关系。这一结果对改善半导体元件中薄膜的温升是有帮助的。     

Interband absorption of light in semiconductor nanostructures

Interband absorption of light in a small semiconductor microcrystal was investigated theoretically within the dipole approximation. An expression for the light-absorption coefficient was derived for the situation where the polarization-related interaction of an electron and hole with the microcrystal surface is dominant. It is shown that the edge of absorption in a microcrystal shifts to shorter wavelengths if the polarization-related interaction of electrons and holes with the microcrystal surface is taken into account. It is ascertained that the absorption edge for small microcrystals is formed by two transitions comparable in intensity; these transitions occur from different levels of size-related quantization for a hole to the lower level of size-related quantization for an electron.