In situ ageing, a development of the in situ techniques for building-in-reliability

A wafer level in situ accelerated ageing method is proposed. A development of in situ techniques for building-in approach to reliability is introduced, because “in situ” does not refer to the electrical testing during the ageing but it is referring to the ageing process itself. A He-Ne laser irradiation of the reverse biased junction is used for accelerating the local degradation by deep level generation currents - the hot spots formation. The efficiency of the method for wafer reliability monitoring was experimentally proved on RF power transistors.     

注入与原位掺杂ETSOI PMOSFETs性能模拟分析

利用TCAD对注入掺杂和原位掺杂ETSOI PMOSFETs进行模拟仿真分析。用从模拟中提取出来的关键特性参数进行对比,以此分析它们性能优劣。在Vtsat一样时,25 nm 栅长注入掺杂器件Ion比原位掺杂的要大200 uA/um左右。同时,9~11 nm Tsi注入掺杂器件的DIBL和SSsat也要小30~50 mV/V 和 6.3~9.1 mV/dec。在栅长为15 nm时,原位掺杂器件的ΔVtsat为-31.8 mV/nm,而注入掺杂器件却仅有-6.8 mV/nm。这些仿真结果表明通过注入得到的ETSOI PMOSFET器件性能比原位掺杂的性能更好,更稳定。     

Degradation kinetics of ultrathin HfO2 layers on Si(1 0 0) during vacuum annealing monitored with in situ XPS/LEIS and ex situ AFM

The evolution of HfO₂(3–5 nm)/SiO₂(0.5 nm)/Si(1 0 0) stacks during vacuum annealing was monitored in situ with the combination of X-ray photoelectron spectroscopy and low energy ion scattering techniques and supplemented with atomic force microscopy analysis to investigate the mechanism that triggers HfO₂ degradation with Hf silicide formation. The reduction of SiO₂ interfacial layer and the formation of local paths for SiO escape into vacuum are believed to be critical at vacuum annealing above T > 850 °C for the reaction between HfO₂ and Si to start and eventually lead to the degradation of the former.     

The Stark shift of the hole states in separate InAs/GaAs quantum dots grown on (100) and (311)A GaAs substrates

Deep-level transient spectroscopy is used to study charge-carrier emission from the states of separate quantum dots in InAs/GaAs p-n heterostructures grown on (100)-and (311)A-oriented GaAs substrates in relation to the reverse-bias voltage U. It is established that the structures under consideration exhibit different bias-voltage dependences of the Stark shift for the energy levels of the quantum-dot states on the value of U.     

Quantification of creep strain in small lead-free solder joints with the in situ micro electronic-resistance measurement

Single shear lap creep specimens with a 1 mm² cross sectional area (similar in size to small lead-free solder joints used in electronic packaging and jointing) between thin copper strips were developed and fabricated using lead-free solder (Sn–3.5Ag) to quantify their creep strain with in situ micro electronic-resistance measurement. Where the solder joints’ micro electronic-resistance is in situ measured by an electronic testing system (tailor-made for the micro electronic-resistance and stress measurement) and recorded by a PC via serial port, then all data of micro electronic-resistance and elapsing time are formed in curves. They are used to describe the solder joints’ micro electronic-resistance and electronic-resistance strain varied with time. Most of curves can reveal the continual development of damage and fracture mechanisms which are consistent with observations generated by literatures. The quantitative relationship between electronic-resistance strain and mechanical-creep strain was proved theoretically using a mathematic model. These mean that the in situ micro electronic-resistance measurement can be used as an alternative quantification of creep strain in small lead-free solder joints. Thus, provide an alternative and simplified evaluation method about the reliability of a solder joint.     

相干泵浦微腔光孤子基础与双光梳应用（特邀）

光学孤子是指一种通过非线性折射率势阱维持脉冲形状不变的光波,它广泛存在于光纤、飞秒激光器、参量振荡器等系统中。近年来,人们在相干泵浦下的高Q值微腔中也观测到了光孤子,这为研究光孤子性质提供了新的实验平台。又因为微腔光孤子在频域上对应高重频的光学频率梳,微腔光孤子的诞生也极大地推动了小型化光学频率梳的发展。微腔光孤子频率梳已经可以实现自参考锁定;这使得片上集成的光频合成器、光原子钟、波分复用光源、微腔光谱仪、微腔激光雷达等众多应用成为了可能。文中介绍了微腔光孤子的产生基础,特别是光孤子相互作用相关的研究,还讨论了基于微腔的双光梳测量在高速成像与中红外气体光谱分析上的应用。     

Structure of heterointerfaces and photoluminescence properties of GaAs/AlAs superlattices grown on (311)A and (311)B surfaces: Comparative analysis

The photoluminescence properties of type II GaAs/AlAs superlattices grown on the (311) surface are determined by their polarity. Previous HRTEM investigations demonstrated a corrugation (with height of 1 nm and period of 3.2 nm) of both GaAs/AlAs and AlAs/GaAs interfaces in samples grown on the (311)A surface. In the present study, a lateral periodicity of 3.2 nm is also revealed in HRTEM images of a superlattice grown on the (311)B surface and in their Fourier transforms. However, this periodicity is poorly pronounced, which is due to fuzzy corrugation and the presence of a long-wavelength (>10 nm) disorder. Photoluminescence spectra of the GaAs/AlAs superlattice on the (311)A surface are strongly polarized relative to the direction of interface corrugation, in contrast to the (311)B superlattice, in which the corrugation is weakly pronounced. It was found that the strong mixing between the Θ and X minima of the conduction band, occurring only in sublattices with strongly corrugated interfaces, allows generation of bright red luminescence at 650 nm up to room temperature. The distinctions revealed between the superlattices grown on the (311)A and (311)B surfaces confirm that it is precisely the interface corrugation, and not crystallographic orientation, that governs the optical properties of (311) superlattices.     

高次离轴凸非球面反射镜组合加工（特邀）

为提高离轴三反消像散（TMA）光学系统中次镜的制造效率和精度,开展了离轴凸非球面反射镜组合加工和零位检测的研究工作。首先,介绍了方形(298 mm×264 mm)高次离轴凸非球面反射镜的光学参数、技术指标和总体加工路线;其次,提出了铣磨加工工艺策略以及基于气囊和沥青的小磨头组合加工工艺;最后,阐述了光学零件抛光阶段采用的背部透射零位补偿检测法和Offner型零位补偿器,并采用光线追迹法对镜片的零位补偿检验面形畸变进行了矫正,最终面形RMS值为0.025λ （λ=632.8 nm）,满足技术指标要求。上述组合加工工艺和背部透射零位补偿检测方案可以显著提升高次离轴凸非球面反射镜的加工精度和效率。     

The growth of (InGa)As quantum wells on GaAs(111)A, (211)A and (311)A substrates

The ability to grow high quality (InGa)As on the (111)A surface is essential for the production of a wide range of optoelectronic devices, but the topic has so far received little attention. What work there has been shows it to be highly problematic, reflected in the very broad photoluminescence (PL) peaks observed for GaAs:(InGa)As multiple quantum well structures. The origin of this broadening is unclear but is certainly related to the difficulty in choosing appropriate conditions for the growth of III-Vs on the (111)A surface. We have undertaken a study of the growth of (InGa)As on the GaAs(111)A, (211)A and (311)A surfaces with the goal of achieving high quality quantum well structures, the test being the ability to obtain narrow PL line widths. We have demonstrated that 80 Å 15% InGaAs(111)A single quantum wells with 12K PL peak widths of less than 8 meV can be obtained by growth at 400°C under a V:III ratio of 5:1.     

Polydisalicylidene azomethyne/Si(GaAs) heterojunctions: Development and properties

An athermal nonvacuum technology was suggested and implemented, and nonclassically polyconjugated polydisalicylidene azomethyne/Si(GaAs) heterojunctions were fabricated for the first time. It was found that the highest photosensitivity of these heterojunctions is attained upon exposure to light in the spectral range of 1–3.5 eV of the side of thin polymer films. It was concluded that new heterojunctions can be used as broadband photoconverters of optical radiation.     

A VLSI structure forX(modm) operation

High-computing speed and modularity have made RNS-based arithmetic processors attractive for a long time, especially in signal processing, where additions and multiplications are very frequent. The VLSI technology renewed this interest because RNS-based circuits are becoming more feasible; however, intermodular operations degradate their performance and a great effort results on this topic. In this paper, we deal with the problem of performing the basic operationX(modm), that is the remainder of the integer divisionX/m, for large values of the integerX, following an approximating and correcting approach, which guarantees the correctness of the result.We also define a structure to computeX(modm) by means of few fast VLSI binary multipliers, which is exemplified for 32-bit long numbers, obtaining a total response time lower than 200 nsec. Furthermore, such a structure is evaluated in terms of VLSI complexity and area and time figuresA=(n ² T _m ² ) andT=(T _M ) for the parameterT _M in are derived. A simple positional-to-residue converter is finally presented, based on this structure; it improves some complexity results previously obtained by authors.This work has been supported by the National Program on Solid-State Electronics and Devices of the Italian National Research Council.     

Optical properties of GaAs/AlAs superlattices grown on (311)A GaAs surfaces

We present a temperature-dependence photoluminescence of (GaAs)₅/(AlAs)₅ superlattice grown on (311)A-oriented semi-insulating substrate by molecular beam epitaxy. The temperature dependence reveals an anomalous decrease of the PL width, which is explained in terms of phonon-assisted thermal activation of localized excitons.     

The maximal PN sequences over GF(p)

In this paper analysis of the maximal pseudorandom sequences (PN sequences) over a Galois Field GF(p) is given. The first part of the paper deals with the properties of the sequences of vectors generated over GF(p). In the second part the autocorrelation function of the pseudorandom sequences is discussed.     

The form of the profile of heterointerfaces in (311)Ga GaAs/AlAs structures

The steady-state photoluminescence and kinetics of photoluminescence of the (100)-oriented and (311)Ga-oriented type II GaAs/AlAs superlattices are studied under the effect of the electric field of the surface acoustic wave. It is found that, in the (100)-oriented structures, the drop of intensity of steady-state photoluminescence and acceleration of photoluminescence kinetics are independent of the direction of the electric field of the surface acoustic wave with respect to crystallographic directions, while in the (311)Ga-oriented structures these effects are anisotropic. It is shown that all variations in the steady-state photoluminescence and in kinetics of photoluminescence of (100)-oriented and (311)Ga-oriented structures under the effect of the electric field of the acoustic wave are associated with transfer and capture by the nonradiative recombination centers of nonequilibrium charge carriers, which are initially localized in wide quantum wells formed by fluctuations of the thickness of the layers of the structures. From the obtained experimental data, the parameters of the profile of heterointerfaces of the (311)Ga GaAs/AlAs superlattices are determined. It is established that the lateral sizes of microgrooves in the [011] direction on the direct and inverse heterointerfaces of the (311)Ga superlattices exceed 3.2 nm, while the modulation of the thickness of the AlAs layers is from 0.8 to 1.2 nm.     

Formation and characterization of (CdZn)S films and (CdZn)S/Cu2s heterojunctions

The present status of (CdZn)S/Cu₂S thin film solar cells is reviewed. A new source design has been used to improve the (CdZn)S films. Light reflection loss has been reduced to ∼ 5% by texturing the (CdZn)S surface prior to Cu₂S formation. Using 90% transparent grids, current densities over 16 ma/cm² and open circuit voltages over 0.7 volts have been obtained, with a best power conversion efficiency of 6.29%.     

InGaAs/GaAs vertical-cavity surface-emitting lasers on (311)B GaAssubstrate

InGaAs/GaAs vertical cavity top-emitting dielectric-mirror surface-emitting lasers have been fabricated on a (311)B GaAs substrate. The threshold current was 25 mA at a lasing wavelength of 0.97 μm under pulsed operation at room temperature. The output was linearly polarised in the [2¯33] direction     

Planar-doped n-type InAlAs/InGaAs MODFETs on InP(311)A substratesby molecular beam epitaxy

N-type doping of silicon in InAlAs/InGaAs/InP modulation-doped field effect transistor (MODFET) structures grown by molecular beam epitaxy (MBE) for the (311)A orientation has been achieved by using the planar-doping technique. An electron mobility as high as 50000 cm² V-s with a sheet carrier concentration of 1.9×10¹²/cm² at 77 K is reported. MODFETs with 1.2-μm gate length exhibit an extrinsic transconductance of 400 mS/mm and a maximum drain current of 485 mA/mm. The results are comparable to those of MODFETs grown on (100) InP substrates. The results point to the possibility of making p-n multi layer structures with all-silicon doping     

Is the be incorporation the same in (311)A and (100) AlGaAs?

The incorporation of the Be acceptor in Al_xGa_{1 − x}As grown by molecular beam epitaxy on (100) and (311)A oriented substrates is investigated by photoluminescence and electrical measurements. Values of the Be binding energy slightly lower than the commonly accepted ones have been found: 32 ± 4 meV at x 0.24. The incorporation efficiency is slightly greater in (311)A than in (100) oriented AI_xGa_{1 − x}As. The Be doping of (311)A oriented AI_x-Ga_{1 − x}As produces materials of higher electrical and optical properties than the Be doping of (100) oriented Al_xGa_{1 − x}As.     

The growth of high mobility heterostructures on (311)B GaAs

We demonstrate that the (311)B surface of GaAs can be used for the fabrication of high mobility (μ 2.4 × 10⁶ cm² V⁻¹ s⁻¹) two-dimensional electron gases, in which the mobility is found to be anisotropic with μ_{[ 33]} > μ_{[01 ]}. This paper reviews the magneto-transport properties of the (311)B system and sheds light on the nature of the scattering mechanisms determining the electron mobility. These results are of particular relevance to the current discussion of the nature of the {311} surface.

It is well known that a similar mobility anisotropy exists in hole gases grown on the (311)A surface, although attempts to interpret such results are complicated by the anisotropic and non-parabolic nature of the valence band structure. For electron gases grown on the (311)B surface we demonstrate experimentally (with ballistic focusing) that the Fermi surface is isotropic, leading to the conclusion that the most likely cause of the mobility anisotropy is anisotropic interface roughness scattering. This is also confirmed by measurements of mobility as a function of carrier density, which can be fitted by a simple interface roughness scattering theory.

Further experiments have demonstrated that ballistic quantization can be observed in both [ 33] and [01 ] directions, despite the large differences in anisotropic mobility.     

红外高光谱遥感成像的技术发展与气体探测应用（特邀）

相对可见光和短波红外谱段来说,在红外谱段进行高光谱遥感成像具有独特优势,特别是在资源勘查、地表环境监测、大气环境监测、军事侦察方面。尽管当前红外高光谱成像仪主要以机载为主,还未实现星载,然而国内外相关机构从未放弃推进红外高光谱遥感的星载化。文中首先分析了国内外典型的红外高光谱成像仪的设计、实现与技术指标,从光谱分辨率、空间分辨率、辐射分辨率三个核心指标总结了现有红外高光谱成像仪的技术特点、存在问题和解决途径。未来很长的一段时间内,红外精细分光、低暗电流焦平面探测器、低温光学与背景抑制仍然是红外高光谱成像仪研制所要解决的核心问题。在此基础上,文中重点介绍了在远距离气体探测方面的应用,并分析了其独特优势。最后,展望了红外高光谱成像技术的发展方向。