Minority carrier diffusion lengths in bulkn-type gaas

Minority carrier hole diffusion lengths in as-grown and Ni- or Cu-diffused bulkn-GaAs, both LEC and HB, having carrier concentrations in the range 10¹⁶-10¹⁷cm⁻³ have been studied by surface photovoltage methods and trap concentrations determined by DLTS measurements. Data are available for a wide range of specimens and therefore a method of correlation ofL _p with electron trap concentrations has been developed that allows easy identification of the dominant recombination center. This is determined to be the level at aboutE _c -0.40 eV, termed EL5 in earlier studies of electron traps.     

Effects of contact metals on minority carrier diffusion lengths in GaAs

Contact technology for GaAs involves optimizing such factors as contact resistance or Schottky barrier height, alloy cycle conditions, thermal ageing, adhesion, and ease of high resolution processing. Minority carrier properties may be significantly degraded by in-diffusing contact metals. At typical alloying conditions of 10 sec at 500° C, Ni diffuses at least 10 μm and reduces the hole diffusion length (L_p) in vapor phase epitaxial GaAs from 4.4 to 1.7 ym. At 600°C, L_p becomes 1.0 μm. Other metals, such as Fe, Pt, and Cr, significantly improve L_p in VPE GaAs. L_p increases from 3.0 to 5.0 μm for an Fe diffusion of 5 minutes at 500°C. These improvements may be due to interaction of in-diffused Fe with recombination centers, such as Ga vacancy complexes or Ni. Fe causes increases in minority carrier diffusion lengths also in n and p type ingot GaAs, though 800 – 900°C diffusions are required and at these temperatures the doping is significantly changed by Fe acceptors.     

Minority carrier diffusion lengths in liquid phase epitaxial InGaAsP and InGaAs

Minority carrier diffusion lengths were determined for InGaAsP and InGaAs layers grown by liquid phase epitaxy on (100)-InP substrates by measuring the variation of the short circuit photocurrent as a focussed laser beam was scanned along a beveled (~1°) p-n junction. The effect of lattice-mismatch on the hole diffusion length (λ_p) for n-type unintentionally doped InGaAsP layers (λg=1.15 μm) was investigated for mismatch values from -0.25% to +0.31%, with the longest diffusion length (L_p = 1.5 μm) occurring when the epitaxial layer was lattice-matched to the substrate. As the amount of mismatch increased, L_p decreased. Electron diffusion lengths, L_n, were determined for lattice-matched quaternary and ternary layers grown from Zn doped melts over a wide range of hole concentrations. At the lowest hole concentrations, p = 3 × l0¹⁵ and 1.4 × 10¹⁶ cm⁻³, the electron diffusion lengths were 3.5 and 2.5 μm for the quaternary and ternary, respectively. As the hole concentration increased, L_n decreased and at the highest concentration (p = 5 × 10su18,cn⁻³) L_n was 0.13 μm for InGaAsP and 0.83 un for InGaAs.     

Study of minority carrier diffusion lengths in photoactive layers of multijunction solar cells

A technique for determining a minority carrier’s diffusion length in photoactive III–V layers of solar cells by approximating their spectral characteristics is presented. Single-junction GaAs, Ge and multi-junction GaAs/Ge, GaInP/GaAs, and GaInP/GaInAs/Ge solar cells fabricated by hydride metal-organic vapor-phase epitaxy (H-MOVPE) have been studied. The dependences of the minority carrier diffusion length on the doping level of p-Ge and n-GaAs are determined. It is shown that the parameters of solid-state diffusion of phosphorus atoms to the p-Ge substrate from the n-GaInP nucleation layer are independent of the thickness of the latter within 35–300 nm. It is found that the diffusion length of subcells of multijunction structures in Ga(In)As layers is smaller in comparison with that of single-junction structures.     

Determination of diffusion lengths in organic semiconductors: Correlation with solar cell performances

Organic semiconductors are promising candidates for future applications in solar energy conversion. Recent investigations of bulk heterojunction (BHJ) semiconductors have suggested a density of states and transport mechanisms by multiple trapping close to those observed in disordered inorganic thin films. That is why we have applied to BHJ thin films experiments that are currently used for disordered semiconductors. In addition to the steady state photoconductivity we have tested the ability of the steady state photocarrier grating (SSPG) technique to provide information on the minority carrier diffusion length. We found that SSPG can be applied to P3HT:PCBM thin films leading, for the best sample, to a diffusion length of the order of 125 nm. From the comparison of the transport parameters obtained on thin films with the performances of the devices integrating the latter, we conclude that SSPG is a very powerful tool for optimizing the BHJ thin film properties before their incorporation in solar devices.     

激光全息干涉法测量维生素B6的扩散系数

为了研究维生素B6的扩散行为,采用了激光全息干涉法,得到了298.15K时不同浓度维生素B6在水溶液和生理盐水中的扩散系数。结果表明,维生素B6在水溶液中的扩散系数随着溶质浓度的增大一直下降,而在生理盐水中则呈现先上升后下降的趋势。这对维生素B6的医学应用具有重要的参考价值。     

Measurement of lateral dopant diffusion in thin silicide layers

The lateral diffusion of dopants in silicides was studied using a sensitive Schottky-barrier test structure that relies on changes in the I-V characteristic of a silicide-polysilicon interface due to dopant diffusion from the doped silicide into the polysilicon. The process flow of the test structure makes the device readily adaptable to all deposited or reacted silicides. The test structure was used to measure the diffusivity of B, As, and P in WSi₂, TiSi ₂, and CoSi₂ at temperatures from 750 to 1000°C. No measurable lateral diffusion of B in TiSi₂ was observed. In all the other cases, diffusion was several orders of magnitude higher than in silicon. These results should aid the development of process flows to prevent device degradation due to the lateral diffusion of dopants in the silicide layer     

Measurement of the base diffusion profile of a narrow-basewidth transistor

A technique for routinely determining the intrinsic base diffusion profile in a narrow-basewidth transistor is described. The technique involves the fabrication of a novel Van der Pauw device and the subsequent measurement of the sheet resistance and Hall coefficient of the base region. Diffusion profiles measured in a shallow double-diffused arsenic-emitter boron-base transistor structure by this technique are reported.     

用Z-80单板机控制激光测微仪自动检测

激光谢微仪可无接触地测量直径为几微米～几十微米的细丝。在Z-80单板机的控制下，可将一轴成千上万米长的细丝从头至尾进行逐点测量。并将总长和各种超差长度及其所占百分比等数据打印出来，以便评定该轴细丝的质量等级。     

Measurement of diffusion length of holes in α-Si:H

The present paper reports the results of a study in the diffusion length of holes in α-Si:H by surface photovoltage using a metal (Ni) Schottky barrier. The change of field-assisted hole transport with bias light was observed. It is believed that measurement of the diffusion length by this method may become a useful way of evaluating and improving the quality of α-Si:H.     

Measurement of dispersion using short lengths of an optical fiber and picosecond pulses from semiconductor film lasers

Group velocity dispersion spectra have been determined for 7.8-m lengths of a single-mode optical fiber. The dispersion spectra are derived from measurement of the transit delay time of picosecond pulses (4-10 ps) from optically pumped ultrashort cavity semiconductor film lasers. The delay time spectra have been measured to 1 ps precision over the range from 1.11 to 1.53 μm for single-mode step-index and quadruple-clad fibers. This is the highest temporal resolution achieved for any pulse delay measurement in optical fibers. The resulting dispersion spectra are in good agreement with measurements made for the same fibers by other techniques.     

Measurement of minority carrier lifetime and diffusion length in silicon epitaxial layers by means of the photocurrent technique

A new method for the determination of minority carrier lifetime and diffusion length in thin silicon epitaxial layers was developed. Using a transparent MIS structure the surface recombination velocity was reduced below 25 cm/s. This method makes possible to determine minority carrier lifetime and also diffusion length much greater than the thickness of the epitaxial layer.     

Electrical lengths of stripline bends

The effect of curvature on the resonant frequencies of various stripline circular rings is investigated both theoretically and experimentally. From these results, an expression is derived which enables the electrical length of a bend, derived from the arithmetic-mean length, to be corrected to allow for the curvature.     

1.55 micrometer ridge DFB laser integrated with a buried-ridge-stripe dual-core spot-size converter by quantum-well intermixing

A ridge distributed feedback laser monolithically integrated with a buried-ridge-stripe spot-size converter operating at 1.55 micrometre wavelength was successfully fabricated by means of low-energy ion implantation quantum-well intermixing and dual-core technologies. The passive waveguide was optically combined with a laterally exponentially tapered active core to control the mode size. The devices emit in a single transverse and single longitudinal mode with a sidemode suppression ratio of 38.0 dB. The threshold current was 25 mA. The beam divergence angles in the horizontal and vertical directions were as small as 8.0 degree X 12.6 degree, respectively, resulting in 3.0-dB coupling loss with a cleaved single-mode optical fiber.     

基于BP神经网络的导线自动检测仪的模型建立

人工神经网络广泛应用于函数逼近、图像处理、自动控制、模式分类等领域。针对反射脉冲导线自动测量仪的高精度建模困难,提出采用BP神经网络解决的方法。实验和仿真表明,采用BP网络能很好的得到导线测长的模型。从而很大程度上提高了该仪器的测量精度。     

Measurement of the diffusion length of minority charge carriers using real Schottky barriers

The characteristic features of the field dependence of the short-circuit photocurrent of real Schottky barriers based on strongly doped semiconductors under conditions of an oscillatory dependence of the light absorption coefficient a on the field intensity in the space-charge region and the photon energy (hν>E _g ) are analyzed. An analytical expression is obtained for the dependence of the photocurrent on the thickness W of the space-charge region when the condition αW≪1 is satisfied. An improved method is proposed for determining the diffusion length of minority charge carriers by analyzing the dependence I _p (W) in the spectral region satisfying the conditions of applicability of the expressions obtained. Some improvements are also made in the method for distinguishing the capacitance of the space-charge region from the high-frequency capacitance of a real Schottky barrier. The method is tested on structures Au-GaAs with N _d =4.5×10¹⁶–1×10¹⁸ cm⁻³. The method of determining L is checked independently on the basis of a theoretical descripion of the spectral dependence of the quantum efficiency of the structure. Fiz. Tekh. Poluprovodn. 31, 781–785 (July 1997)     

Noninvasive measurement of biological information by nuclear magnetic resonance: Measurement of relaxation time of a particular target by magnetic focusing method

In order to clarify the possibility of detecting cancer noninvasively by the measurement of the relaxation time, model experiments were performed by applying our proposed magnetic focusing method to conventional nuclear magnetic resonance (NMR) techniques. It was made clear that the relaxation time of a particular target was selectively estimated from the proximity of the target by this method.     

Determination of the oxygen diffusion profile in polycrystalline lead selenide layers using nuclear microanalysis

Rutherford backscattering and nuclear reactions are used to study the concentration profiles of elements in oxidized samples of lead selenide (PbSe). An interpretation of experimental data in the context of the theory of diffusion over the grain boundaries is suggested.     

微米光栅加速度计闭环检测技术优化与设计

提出一种基于Pound-Drever-Hall(PDH)调制技术的新型闭环控制方法,优化了微米光栅加速度计的信噪比和静态检测精度.采用电磁驱动实现自校准和反馈控制,相对于静电驱动降低了功耗提升了反馈效率,解决了开环检测方式下测量范围和灵敏度不可兼得的难题.对系统光学输出的干扰源进行本质分析,通过将闭环误差信号调制到高频...