Hydrogen in the near-surface of crystalline silicon

Abstract

Real-time electric field drift experiments, in-situ capacitance-voltage profiling, deep-level transient spectroscopy and nuclear reaction analysis have been used to monitor hydrogen motion and passivation processes in silicon. Spontaneous hydrogen injection and very fast migration has been detected in the near-surface region of various Schottky barriers and p-n junctions. The effective hydrogen diffusivity is about 10^?8 cm²/s at 400 K in agreement with the estimated value obtained by extrapolation from the high-temperature diffusivity data. The results of real-time in-situ measurements clearly demonstrate that the fast diffusing protons are involved in the hydrogenation processes of both shallow and deep levels. The possible physicochemical mechanisms for the observed spontaneous hydrogen injection which results in unintentional hydrogenation of the subsurface of silicon, and probably other semiconductors, are discussed.     

Energy relaxation and thermalization of hot electrons in quantum wires

We develop a theory of energy relaxation and thermalization of hot carriers in clean quantum wires. Our theory is based on a controlled perturbative approach for large excitation energies and emphasizes the important roles of the electron spin and finite temperature. Unlike in higher dimensions, relaxation in one-dimensional electron liquids requires three-body collisions and is much faster for particles than holes which relax at nonzero temperatures only. Moreover, comoving carriers thermalize more rapidly than counterpropagating carriers. Our results are quantitatively consistent with a recent experiment.     

Electron relaxation and transport in nanostructured and bulk silica

Processes of ballistic and hot electron relaxation in extended bulk as well as nanostructured silica have been analyzed by means of a phonon-based scattering model and respective Monte-Carlo computer simulation. Optical as well as acoustic phonons are taken into account. Trajectories of electrons and their energy attenuation in nanostructured silica are additionally affected by scattering processes at the grain boundaries between the nanoparticles, i.e. by surface phonon as well as potential scattering. Moreover, a flatter conduction band and a higher effective electron mass have been taken into account too. According to these calculations, electrons with an initial energy of several eV, but still below the valence band ionization threshold, were thermalized in 50–300 fs increasing with the silica grain size from 1 nm up to bulk material. The electron emission probabilities over the surface barrier into vacuum are extended up to depths of 60–100 nm, respectively, increasing with enhancement by an electric field.     

Energy dissipation of heated electrons in silicon dioxide layers

The field and thickness dependence of the conductivity, charge state, and electroluminescence of Si-SiO₂ structures is investigated with the aim of studying the energy-dissipation mechanisms of electrons heated by an electric field in SiO₂ films. It is shown that, as well as the previously known dissipation channels (interaction with the phonon subsystem and impact ionization in the SiO₂ volume, with characterisic energy losses ₁<0.153 eV and ₂>9 eV, respectively), account must also be taken of processes of defect excitation at the Si-SiO₂ boundary, which are accompanied by radiative relaxation in the electroluminescence bands and characterized by intermediate energy-loss values (₁<<₂).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 36–40, January, 1991.     

The emission of electrons from hot silicon surfaces

The emission of electrons from hot silicon surfaces is reviewed in an effort to present a summary of the state of research in this field. The theoretical aspect of the problem is outlined briefly, and experimental results covering the temperature and field dependence of the saturation current density, as well as the anisotropy and the energy distribution of the emission are presented.     

Remote polar phonon scattering for hot electrons in Si-inversion layers

The effect of the remote interfacial phonon (R.I.P.) scattering on the carrier drift velocity v is evaluated in function of the effective mobility, i.e. in function of the surface roughness. A perturbation theory using the experimental ν?F relation as a zero order approximation is used to calculate the contribution of the R.I.P. scattering. The calculation shows that the influence of this phonon mode scattering on the transport properties in Si-inversion layers is dependent on the carrier low field mobility and is of the order of 10%. The R.I.P. scattering is particularly significant in the warm electron regime, having no consequence on the saturation velocity.     

Determination of the g-factor of electrons in N-type silicon surface inversion layers

The g-factor of conduction electrons in the surface inversion layer on a silicon (100) surface has been determined using the tilted magnetic field method developed by Fang and Stiles.The value of (m¹/m₀)·g at the fixed magnetic field was independent of surface carrier density n_s, whereas it had a sharp peak at about 97 koe. At strong magnetic field limit the value was constant and 0.4. If we take the effective mass of conduction electrons in the inversion layer on the (100) surface as 0.2m₀, the g-factor is about two which is the same as that for conduction electrons in bulk silicon.     

Intervalley transfers of hot electrons in silicon below 77 K

Intervalley rate transfer along 〈100〉 directions is deduced from conductivity measurements versus electric field for different impurity concentrations N_D-N_A at lattice temperatures T ? 77 K. The maximum rate transfer plotted versus T reaches 1 at T < 25 K and does not depend on N_D-N_D for N_D-N_A ? 2 × 10¹⁴crmcm^?3.     

Monte Carlo simulation of two-dimensional hot electrons in n-type Si inversion layers

Monte Carlo simulation is carried out to study high field transport of the two-dimensional electron gas formed on the (100) surface of silicon. Good agreement is obtained between the measured and calculated results. The saturation of the drift velocity is found to depend on the magnitude of the first-order intervalley phonon scattering.     

Inter- and intra-subband relaxation of hot electrons in GaAs/AlGaAs quantum wells

In this work, we have studied the inter- and intra-subband scattering of hot electrons in quantum wells using the hot electron-neutral acceptor luminescence technique. We have observed direct evidence of the emission of confined optical phonons by hot electrons excited slightly above the n=2 subband in GaAs/Al_0.37Ga_0.63As quantum wells. Scattering rates of photoexcited electrons via inter- and intra-subband LO phonon emission were calculated based on the dielectric continuum model. We found that, for wide wells with the Al composition of our experiments, both the calculated and experimental results suggest that the scattering of the electrons is dominated by the confined LO phonon mode. In the calculations, scatterings among higher subbands are also dominated by the same type of phonon at well width of 10 nm.     

Hot electrons in silicon dioxide: Ballistic to steady-state transport

Hot electron transport in silicon dioxide is examined with emphasis on current experimental and theoretical results. For oxide layers thicker than 100 Å, steady-state transport has been shown to control the carrier flow at all fields studied. The transition from a nearly thermal electron distribution at electric fields less than approximately 1.5 MV/cm to significantly hot distributions with average energies between 2 and 6 eV at higher fields of up to 16 MV/cm is discussed. The significance of nonpolar phonon scattering in controlling the dispersive transport at higher electric fields, thereby preventing runaway and avalanche breakdown, is reviewed. The transition from ballistic to steady-state transport on very thin oxides layers of less than 100 Å in thickness and the observation of single phonon scattering events are also discussed.     

Simulation of fast electron transport in silicon

A model for estimating the number of electrons produced as a result of the fast-ion-surface interaction is proposed. The dependence of the number of electrons emitted by the surface in collisions between fast protons and silicon as a function of the angle of incidence and as a function of the layer depth where the electron was produced is analyzed.     

利用渡越辐射研究超热电子在固体靶中的输运过程

为了探索超热电子的输运过程，在100 TW掺钛蓝宝石飞秒激光器上利用光学CCD相机和OMA光学多道分析仪，分别在靶背表面法线方向测量了光发射空间分布图案和光谱. 实验测量结果显示，光发射空间分布图案呈圆盘状，在圆盘中明亮而强的光信号呈局部化分布，该现象表明，超热电子在输运的过程中存在成丝效应，引起严重的不稳定性；光发射光谱在3倍频和3/2倍频附近出现尖峰，分别是3次谐波和3/2次谐波，这一现象归因于超热电子束在传输的过程中产生的微束团而引起的相干渡越辐射(CTR)；光发射光强随靶厚度的增加而减小. 关键词： 超热电子 相干渡越辐射 输运 不稳定性     

超热电子的产生与输运背向辐射的实验研究

报道了在100TW fs激光器上采用电子磁谱仪和光学CCD积分成像相机分别对激光-固体靶相互作用在靶背方向产生的超热电子能谱及其光学渡越辐射进行的测量.能谱测量结果显示:超热电子能谱呈单温类-麦克斯韦分布,拟合的温度为107 keV;光学渡越辐射(OTR)测量结果显示:OTR是由于超热电子输运穿越固体靶所致,而辐射区域呈圆盘状、有发散角、有光强分布;如果考虑超热电子的产生和加热机制,则占主导地位的加热机制是共振吸收对电子的加热.     

超热电子的产生与输运背向辐射的实验研究

报道了在100TW fs激光器上采用电子磁谱仪和光学CCD积分成像相机分别对激光-固体靶相互作用在靶背方向产生的超热电子能谱及其光学渡越辐射进行的测量。能谱测量结果显示：超热电子能谱呈单温类-麦克斯韦分布,拟合的温度为107keV;光学渡越辐射(OTR)测量结果显示：OTR是由于超热电子输运穿越固体靶所致,而辐射区域呈圆盘状、有发散角、有光强分布;如果考虑超热电子的产生和加热机制,则占主导地位的加热机制是共振吸收对电子的加热。     

超热电子输运背向光辐射的实验研究

在100TW掺钛蓝宝石飞秒激光器上利用光学CCD相机和光学多道分析仪,分别在靶背法线方向测量了超热电子光辐射的空间分布和光谱.测量结果显示：光辐射空间分布图案呈圆环状,而辐射区域有发散角和光强分布,且包含多种辐射成分.光辐射光谱在800nm附近出现尖峰,是激光的基频(ω₀)波,这一现象归因于超热电子束在输运的过程中产生的微束团而引起的相干渡越辐射(CTR).随着激光能量的增加,CTR光谱峰向红光方向移动,基频波红移的主要原因是由于等离子体临界面的迅速膨胀.如果考虑超热电 关键词： 超热电子 光辐射 共振吸收 红移