Long Lifetime State of Shallow Donor Centres for Silicon Based THz Sources

Impurity centres in high purity silicon with ionization energies 38.32 and 40.09meV are observed by photothermal ionization spectroscopy measurements. Their typical shallow donor characteristics are approved by good agreement with theoretic evaluation under varying magnetic fields. The 2p0 state lifetime of one donor centres are more than 3 times longer than that of phosphorus in the same silicon sample. Compared to phosphorus which has been already successfully exploited to produce silicon-based THz radiations, this shallow donor centre has a pronounced enhancement on lifetime and quality factor of population inversion level. Hence, silicon with this donor centre would be a potential excellent candidate to develop improved silicon-based THz sources.     

ONP Spectroscopy of Defects in Silicon

Optical nuclear polarization technique is used to study metastable properties of the gold donor center in silicon. A model of a deep defect’s symmetry changing C _3V  → C _1h  → D _2d with its charge state (D⁻ → D⁰ → D⁺) is proposed to account for the observed optically induced quenching and regeneration of Au⁰ centers.     

B和H离子顺次注入单晶Si 引起的缺陷及其热演变(英文)

室温下将130 keV,5x1014 cm-2 B离子和55 keV,1x1016 cm-2 H离子单独或顺次注入到单晶Si中,采用横截面试样透射电子显微镜(XTEM)和慢正电子湮没技术(SPAT) 研究了离子注入引起的微观缺陷的产生及其热演变。XTEM观测结果显示,B 和H 离子顺次注入到单晶Si 可有效减少(111) 取向的H板层缺陷,并促进了(100) 取向的H板层缺陷的择优生长。SPAT 观测结果显示,在顺次注入的样品中,B 离子平均射程处保留了大量的空位型缺陷。以上结果表明,B离子本身及B 离子注入所产生的空位型缺陷对板层缺陷的生长起到了促进作用。Abstract:Cz n-type Si (100) wafers were singly or sequentially implanted at room temperature with 130 keV B ions at a fluence of 5x1014 cm-2 and 55 keV H ions at a fluence of 1x1016 cm-2. The implantation-induced defects were investigated in detail by using cross-sectional transmission electron microscopy (XTEM) and slow positron annihilation technique (SPAT). XTEM results clearly show that sequential implantation of B and H ions into Si could eliminate the (111) platelets and promote growth of (100) platelets during annealing. SPATmeasurements demonstrate that in B and H sequentially implanted and annealed Si, more vacancy-type defects could remain in sample region around the range of B ions. These results indicat e that the promotion effect shouldbe attributed to the role of both B and B implanted induced vacancy-type defects.     

离子辐照产生的空位型缺陷对Si中B原子热扩散的影响

使用二次离子质谱仪分析了附加的空位型缺陷对单晶Si中注入B原子热扩散的影响. Si中B原子是通过30keV B离子室温注入而引入的, 注入剂量为2×10¹⁴cm^－2. Si中附加的空位型缺陷通过两种方式产生: 一是采用40或160keV He离子注入单晶Si到剂量5×10¹⁶cm^－2,并经800°C退火1h; 二是采用0.5MeV F或O离子辐照单晶Si到剂量5×10¹⁵cm^－2.结果显示, 不同方式产生的附加的空位型缺陷均能抑制注入的B原子在随后热激活退火中发生瞬间增强扩散效应, 并且抑制的效果依赖于离子的种类和离子的能量. 结合透射电子显微镜和卢瑟福背散射分析结果对以上抑制效应进行了定性的讨论.     

Effects of Additional Vacancy-Like Defects Produced by Ion Impealations on Boron Thermal Diffusion in Silicon

The effects of additional vacancy-like defects on thermal diffusion of B atoms in silicon were investigated by using secondary ion mass spectroscopy. B atoms were introduced into silicon by 30keV B ion implantation at a dose of 2×10¹⁴cm^－2, while the additional vacancy-like defects were produced by two different ways. One was via 40 or 160keV He ion implantation at a dose of 5×10¹⁶cm－2 and followed by an annealing at 800°C for 1h, which produced a well-defined cavity band near the projected range of He ions. The other was via 0.5MeV F or O ion implantation at a dose of 5×10¹⁵cm^－2,which creates excess vacancy-like defects around the 1/2 projected range of F or O ions. Our results clearly show that the additional vacancy-like defects could suppress the boron diffusion during subsequent thermal annealing at 800°C for 30 min. The suppressing effects were found to depend on both the ion type and ion energy. The results were qualitatively discussed in combination with the results obtained by using transmission electron microscopy and Rutherford backscattering spectroscopy.     

Shallow Donor Impurities in Quantum Well WiresIEffects of Image potential

We calculate the shallow donor impurity binding.energies including image potential in quasione- dimensional GaAs/AIAs quantum well wires with rectangular cross section using the variational approach. The results we have obtained show that when impurity ion image potential is considered the variations of binding energy are remarkable, and when the image potentials of impurity ion and electron are considered simultaneously the corresponding variations of binding energy are small. The results also show that the image potential is important, especially when the cross section dimensions of quantum wires become small.     

Shallow States of Donor Impurities at Defective Semiconductor Surfaces

Ground state energies for shallow states of donor impurities at certain idealized defective isotropic semiconductor surfaces are calculated variationally for GaAa surfaces with electrons confined within the semiconductor. Calculations show that impurity states with donor ions located at parts projecting out of surfaces have lower ground state energiea than those with ions located at parts sunk into surfaces.     

Generation Activity and Structural Defects in Near-Surface Silicon Layers

A correlation between the formation of regions of anomalous generation in MOS-structures of silicon and the lattice disturbances of its near-surface layer is studied using the method of relaxation of nonequilibrium capacitance in combination with metallography. It is found that these regions can be formed with a wide range of surface concentrations and charge carrier generation times depending on the oxidation time. The superposition of selective etching patterns and generation-time distribution of a preset wafer segment shows that the formation of regions of anomalous generation is due to the structural lattice disturbances revealed by the Sirtl-etchant as dome-like figures.     

The Shallow Donor Impurity State Near a Polar Crystal Surface

We report the results of a variational calculntion for the ground state of a near surface hydrogenic donor interacting with both surface and bulk longitudinal optical (SO and BO) phonons in polar crystals. In calculation we also consider the effect of the image potentials. The variations of ground state energies and binding energies with R are given for some materials.     

氧化锌量子点浅施主能级增强绿色光致发光光谱的实验证明

利用溶胶-凝胶法制备了粒径在5 nm左右的氧化锌量子点,通过测量氧化锌量子点光致发光光谱、吸收光谱以及荧光寿命得到氧化锌量子点绿光光谱可分为两种且对应不同发光机理。较高能量的绿光光谱是电子由导带底跃迁至氧空穴辐射产生的,而较低能量的则归因于电子由浅施主能级跃迁到氧空位,这种浅施主能级能够增强绿光发射且激发光能量稍小于带隙时绿光光谱相对强度达到最大。其次,实验得到氧化锌量子点的蓝光光谱是由于激发电子从锌间隙能级跃迁至价带产生。该研究提出并分析了氧化锌量子点绿光光谱的两种发光机制,可为其在光学方面的应用提供参考。     

Model for Thermal Oxidation of Silicon

Technical Physics - Nanometer-thick silicon oxide films are needed for miniaturization and increase in the working rate of electronic devices. Interpretation of the initial stages of silicon...     

高能氩离子辐照硅产生的缺陷研究

在室温下750MeV氩离子对本征单晶硅进行辐照,通过用正电子湮没寿命测量技术、电子顺磁共振技术以及红外光吸收方法研究了辐照产生的缺陷.结果表明:电中性双空位是辐照产生的主要空位团;在4.3×10¹⁴ions/cm²的高剂量下未见样品发生非晶化转变;虽然在离子射程末端双空位的浓度随剂量的增加而显著增大,但在以电离激发过程为主要能损方式的区域里双空位的浓度基本不变.据此可以认为,电子能损过程对辐照产生的缺陷有退人作用.     

The Ground State Energy of Shallow Donor Impurity Near a Crystal Surface

In this letter we have studied the effect of image potential on the ground state energy of a shallow donor impurity near a sharp surface of a semi-infinite crystal. The energy expression of the system as a function of its position is calculated with the variational method. The results are discussed.     

Electronic States of a Shallow Hydrogenic Donor Impurity in Different Shaped Semiconductor Quantum Wells

The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease withthe increase of the well width and decrease quickly when the well width is small.The binding energy of the ground state increases until it reaches a maximum value,and then decreases as the well width increases. The results are meaningful andcan be widely applied in the design of various optoelectronic devices.     

Unusual X-Shaped Defects in the Silicon Single Crystal Subjected to Four-Point Bending

JETP Letters - Dislocations in single-crystal silicon created by the four-point bending method are investigated using a laboratory X-ray source. Two- and three-dimensional diffraction images in the...     

Temporary Surface Passivation for Characterisation of Bulk Defects in Silicon: A Review

Accurate measurements of the bulk minority carrier lifetime in high‐quality silicon materials is challenging due to the influence of surface recombination. Conventional surface passivation processes such as thermal oxidation or dielectric deposition often modify the bulk lifetime significantly before measurement. Temporary surface passivation processes at room or very low temperatures enable a more accurate measurement of the true bulk lifetime, as they limit thermal reconfiguration of bulk defects and minimize bulk hydrogenation. In this article we review the state‐of‐the‐art for temporary passivation schemes, including liquid immersion passivation based upon acids, halogen‐alcohols and benzyl‐alcohols, and thin film passivation usually based on organic substances. We highlight how exceptional surface passivation (surface recombination velocity below 1 cm s^?1) can be achieved by some types of temporary passivation. From an extensive review of available data in the literature, we find p‐type silicon can be best passivated by hydrofluoric acid containing solutions, with superacid‐based thin films showing a slight superiority in the n‐type case. We review the practical considerations associated with temporary passivation, including sample cleaning, passivation activation, and stability. We highlight examples of how temporary passivation can assist in the development of improved silicon materials for photovoltaic applications, and provide an outlook for the future of the field.

     

Synthesis of Ultrafine Silicon Carbide Powders in Thermal Arc Plasmas

Ultrafine ?-SiC powders are synthesized in thermal plasmas by a reaction between methane and silicon monoxide. The reaction is carried out in an unconfined plasma jet (22.5 kW) operating at atmospheric Ar pressure. High temperatures (> 10 000 K) combined with ultrarapid quench rates (? 106 K/s) of the plasma lead to a high degree of supersaturation of the chemical vapor, resulting in homogeneous nucleation of ultrafine particles. Product characterizations are pursued with X-ray diffraction analysis, X-ray photoelectron spectroscopy (XPS), scanning, and transmission electron microscopy. The maximum SiC yield determined by thermogravimetric analysis (TGA) is 97.3 percent. Particle size analyses show a bimodal distribution with the majority of the particles falling in a size range from 2 to 40 nm. Triangular and hexagonal SiC particles are observed throughout this work and the nucleation and growth of these particles are discussed.