Electron Beam Induced Current Research Articles

Electrical properties of oxygen precipitate-related defects in Czochralski silicon

Oxygen precipitate-related defects in Czochralski (Cz) silicon have been studied by electron-beam-induced current (EBIC) and deep-level transient spectroscopy (DLTS). The EBIC results present that oxygen precipitates combined with dislocations can strengthen carrier recombination. The DLTS data reveals two levels of T 1 (E v + 0.43 eV) and T 2 (E v + 0.26 eV), which are related to the oxygen precipitates and dislocations, respectively. Hydrogen can partly passivate the recombination activity of oxygen precipitates and dislocations, as well as their induced electronic states. The results are of interest for deeply understanding the electronic properties of oxygen precipitates and their induced dislocations in Cz silicon used in the semiconductor industry.

Study of zinc oxide/porous silicon interface for optoelectronic devices

A study of the interface of the ZnO/PSi heterojunction with photoluminescense (PL), cathodoluminescense (CL) and Electron Beam Induced Current (EBIC) is presented. The fabrication process of the heterostructure consisted of three steps; First, it was formed the porous silicon (PSi) layer via electrochemical synthesis, it was followed by the growth of a ZnO thin film onto the Psi layer via RF-magnetron sputtering, Finally, a thermal annealing process at 700 °C was applied on the ZnO/PSi heterojunction device. The PL analysis revealed a widening of the luminescence spectrum (in a range of 350 to 850 nm) due to the application of a thermal annealing process which favored the crystallization of the ZnO/PSi structure. Monochromatic CL images were focused on the two main peaks of the CL spectra at 385 and 436 nm, showing the emission of the ZnO and the ZnO/PSi structure, respectively. EBIC characterization determined the electronic properties of the heterojunction such as deflection zone (50 nm) as well as the hole (Lp=55nm), and electron (Ln=60nm) diffusion lengths. Furthermore, EBIC characterization served to experimentally determined the density of donor impurity atoms in the ZnO film (Nd=3.75x1014cm−3).

Processes of the Reliability and Degradation Mechanism of High-Power Semiconductor Lasers

High-power semiconductor lasers have attracted widespread attention because of their small size, easy modulation, and high conversion efficiency. They play an important role in national economic construction and national defense construction, including free-space communication; industrial processing; and the medical, aerospace, and military fields, as well as other fields. The reliability of high-power semiconductor lasers is the key point of the application system. Higher reliability is sought in the military defense and aerospace fields in particular. Reliability testing and failure analysis help to improve the performance of high-power semiconductor lasers. This article provides a basis for understanding the reliability issues of semiconductor lasers across the whole supply chain. Firstly, it explains the failure modes and causes of failure in high-power semiconductor lasers; this article also summarizes the principles and application status of accelerated aging experiments and lifetime evaluation; it also introduces common techniques used for high-power semiconductor laser failure analysis, such as the electron beam-induced current (EBIC) technique and the optical beam-induced current (OBIC) technique, etc. Finally, methods used to improve the reliability of high-power semiconductor lasers are proposed in terms of the preparation process, reliability screening, and method application.

Understanding SiOx Layer Breakup in poly-Si/SiOx Passivating Contacts for Si Solar Cells Using Precisely Engineered Surface Textures

The contact resistivity of polycrystalline silicon on silicon oxide (poly-Si/SiOx) passivating contacts depends on the formation of pinholes in SiOx for thicknesses ≳1.7 nm. We fabricated these contacts on inverted pyramids and v-grooves in addition to the alkaline-textured random pyramids and planar surface morphologies. The thermal breakup of SiOx was achieved at peak annealing temperatures of 1050 and 1100 °C. SiOx breakup at 1050 °C resulted in pinholes created preferentially at vertices in the inverted pyramids, while at 1100 °C, their formation was random. The density of pinholes was greater in textured samples than in polished samples. Both chemical etching and electron beam-induced current (EBIC) were used to visualize the pinholes, the latter being sensitive only to transport pinholes in the p–n junction but not the n+-n junction. We ascribe this difference in EBIC images based on the contact polarity to differences in the collection probability of the minority carriers generated by the electron beam. Our work demonstrates that texture morphology can be exploited to enable the precise engineering of pinholes in poly-Si/SiOx passivating contacts.

Imaging Dielectric Breakdown in Valence Change Memory (Adv. Funct. Mater. 2/2022)

Dielectric Breakdown Transistors, capacitors, and resistive random-access memory (RRAM) elements have an oxide film at their heart. In article number 2102313, Brian C. Regan and co-workers apply scanning transmission electron microscopy (STEM) electron beam-induced current (EBIC) imaging to RRAM elements cycling in situ. STEM EBIC imaging clearly visualizes otherwise-invisible dielectric breakdown processes occurring in the nominally insulating oxide film.

Replacing tunnel junctions in InP with conduction channels with GaP crystallites

The results of investigations by the method of Electron beam-induced current of p-n-junctions based on InP with GaP crystallites in the space charge region are presented. It is shown that the introduction of crystallites into the space charge region leads to short-circuiting of the p-n-junction. The quality of the material grown on top of the crystallites allows to create of photoactive regions, as evidenced by measurements of the photoluminescence spectra. Keywords: crystallites, tunnel junction, connecting element.

Electron-beam-induced current (EBIC) imaging technique to quicken polysilicon defect localization in MOSFETs

It is demonstrated that EBIC imaging technique is superior in quick localizing polysilicon defect of metal-oxide-semiconductor field-effect transistors (MOSFETs). Once polysilicon leakage phenomena are examined, relying on EBIC imaging analysis, we can rapidly isolate nanoscale defect in tens of microns length range. Although faulty polysilicon is employed by more than one MOSFET, it turns out to be unnecessary to characterize all devices after EBIC imaging analysis. By comparative studies, it is concluded that 2-probe EBIC imaging is preferred for mega-Ohm range resistive defect localization while 1-probe configuration is only applicable for kilo-Ohm range. Nanoprobe I-V measurement of the isolated device uncovers the abnormal electrical characteristic which fairly aligns with EBIC imaging analysis. Focused ion beam (FIB) and transmission electron microscopy (TEM) findings imply the EBIC imaging has submicron level spatial resolution toward resistive defects. Therefore it overcomes traditional limits in terms of technical method and lowers failure analysis (FA) difficulty considerably. Ultimately, a simplified model is proposed to explain the physical mechanism of this application. Our modeling describes the strong dependance of EBIC imaging on hot excess carrier behavior within shallow p-n junction when electron beam (e-beam) penetrates into bulk silicon. The work improves the understanding of excess minority carriers transport properties in p-n junction under scanning e-beam irradiation. And this paper may make EBIC imaging be a more promising way to identify minute material defect of future advanced MOSFET.

Random walk on spheres algorithm for solving steady-state and transient diffusion-recombination problems

Abstract We further develop in this study the Random Walk on Spheres (RWS) stochastic algorithm for solving systems of coupled diffusion-recombination equations first suggested in our recent article [K. Sabelfeld, First passage Monte Carlo algorithms for solving coupled systems of diffusion–reaction equations, Appl. Math. Lett. 88 2019, 141–148]. The random walk on spheres process mimics the isotropic diffusion of two types of particles which may recombine to each other. Our motivation comes from the transport problems of free and bound exciton recombination. The algorithm is based on tracking the trajectories of the diffusing particles exactly in accordance with the probabilistic distributions derived from the explicit representation of the relevant Green functions for balls and spheres. Therefore, the method is mesh free both in space and time. In this paper we implement the RWS algorithm for solving the diffusion-recombination problems both in a steady-state and transient settings. Simulations are compared against the exact solutions. We show also how the RWS algorithm can be applied to calculate exciton flux to the boundary which provides the electron beam-induced current, the concentration of the survived excitons, and the cathodoluminescence intensity which are all integral characteristics of the solution to diffusion-recombination problem.

Thermally propagated Al contacts on SiGe nanowires characterized by electron beam induced current in a scanning transmission electron microscope

Here, we use electron beam induced current (EBIC) in a scanning transmission electron microscope to characterize the structure and electronic properties of Al/SiGe and Al/Si-rich/SiGe axial nanowire heterostructures fabricated by thermal propagation of Al in a SiGe nanowire. The two heterostructures behave as Schottky contacts with different barrier heights. From the sign of the beam induced current collected at the contacts, the intrinsic semiconductor doping is determined to be n-type. Furthermore, we find that the silicon-rich double interface presents a lower barrier height than the atomically sharp SiGe/Al interface. With an applied bias, the Si-rich region delays the propagation of the depletion region and presents a reduced free carrier diffusion length with respect to the SiGe nanowire. This behaviour could be explained by a higher residual doping in the Si-rich area. These results demonstrate that scanning transmission electron microscopy EBIC is a powerful method for mapping and quantifying electric fields in micrometer- and nanometer-scale devices.

Mapping Charge Recombination and the Effect of Point-Defect Insertion in GaAs Nanowire Heterojunctions

Electronic devices are extremely sensitive to defects in their constituent semiconductors, but locating electronic point defects in bulk semiconductors has previously been impossible. Here we apply scanning transmission electron microscopy (STEM) electron-beam-induced current (EBIC) imaging to map electronic defects in a $\mathrm{GaAs}$ nanowire Schottky diode. Imaging with a nondamaging 80 or 200 kV STEM acceleration potential reveals a minority-carrier diffusion length that decreases near the surface of the hexagonal nanowire, thereby demonstrating that the device's charge collection efficiency (CCE) is limited by surface defects. Imaging with a 300 keV STEM beam introduces vacancy-interstitial (or Frenkel) defects in the $\mathrm{GaAs}$ that increase carrier recombination and reduce the CCE of the diode. We create, locate, and characterize a single insertion event, determining that a defect inserted 7 nm from the Schottky interface broadly reduces the CCE by $10\mathrm{%}$ across the entire nanowire device. Variable-energy STEM EBIC imaging thus allows both benign mapping and pinpoint modification of a device's electron-hole-recombination landscape, enabling controlled experiments that illuminate the impact of both extended (one- and two-dimensional) and point (zero-dimensional) defects on semiconductor device performance.

Reliability and failure analysis in power GaN-HEMTs during S-band pulsed-RF operating

This paper reports a reliability study on two technologies of AlGaN/GaN high-electron mobility transistors (AlGaN/GaN HEMTs) (Device “A” and Device “B”). A failure analysis study is conducted on devices stressed under real operating conditions for radar applications. The devices underwent pulsed-RF long ageing tests and after 11,000 h show a degradation in RF and DC performances (Drop of drain current and RF output power, pinch-off shift, decrease of the maximum of transconductance, lateral translation of transconductance, and increase of gate-lag and drain-lag). Hot electron effects are supposed to be the origin of the observed degradations and trapping phenomena within the passivation or GaN layers. Photon emission microscopy (PEM), Optical Beam Induced Resistance Change (OBIRCH), Electron Beam Induced Current (EBIC) measurements concur with this hypothesis. The three techniques reveal a non-uniform response and an inhomogeneous distribution along the gate fingers, in addition to the presence of some localized spots localized on the gate edge either on the drain side or on the source side. Spectral PEM analysis of these spots identifies a native defect that could be related to crystallographic defects such as dislocations or impurities. Atom probe tomography (APT) analysis on the two technologies of AlGaN/GaN HEMTs supports this hypothesis. APT results show the presence of some chemical impurities like carbon and oxygen. These impurities are in relatively significant concentrations in device “A” which could explain the high level of gate-lag and drain-lag in this device compared to device “B”.

Recombination and Charge Collection at Nickel Silicide Precipitates in Silicon Studied by Electron Beam‐Induced Current

Nickel di-silicide layers have attracted scientific interest since the 1990’s as lattice-matched Schottky barriers on silicon and as strong carrier recombination centers when embedded in the silicon. High-resolution electron microscopy and electron beam-induced current are used by Philipp Saring and Michael Seibt (article number 2100142) to show that atomically thin silicide precipitates have properties similar to bulk nickel di-silicide in terms of the Schottky barrier height and electric conductivity. The cover image is an artistic view on processes of recombination and charge collection at thin silicide platelets. Experimental data are shown in front of the silicide’s atomic structure in silicon (image courtesy by L. Kroll).

Imaging Dielectric Breakdown in Valence Change Memory

AbstractDielectric breakdown (DB) controls the failure, and increasingly the function, of microelectronic devices. Standard imaging techniques, which generate contrast based on physical structure, struggle to visualize this electronic process. Here in situ scanning transmission electron microscopy (STEM) electron beam‐induced current (EBIC) imaging of DB in Pt/HfO2/Ti valence change memory devices is reported. STEM EBIC imaging directly visualizes the electronic signatures of DB, namely local changes in the conductivity and in the electric field, with high spatial resolution and good contrast. DB is observed to proceed through two distinct structures arranged in series: a volatile, “soft” filament created by electron injection; and a non‐volatile, “hard” filament created by oxygen‐vacancy aggregation. This picture makes a physical distinction between “soft” and “hard” DB, while at the same time accommodating “progressive” DB, where the relative lengths of the hard and soft filaments can change on a continuum.

Use of passive, quantitative EBIC to characterize device turn-on in 7 nm technology

A novel analysis routine is proposed that visualizes the opening of a transistor channel using Electron Beam Induced Current (EBIC) with a net zero-volt bias across a channel. nFET devices on a 7 nm technology node chip were examined in two different regions of the sample. With varying gate voltage, the device turn-on was clearly evident in the resulting EBIC image. Quantitative analysis of the resulting currents is demonstrated, and shows the channel opening up at voltages earlier than shown by I-V measurement. A mechanism for this difference is proposed. The analysis, also involving a 2-dimensional map of the space, provides opportunities for detecting regional variations in the electrical properties or performance at the high resolutions afforded with a scanning electron microscope (SEM).

Heterostructural perovskite solar cell constructed with Li-doped p-MAPbI3/n-TiO2 PN junction

Traditional P-i-N perovskite solar cells have achieved high efficiency over 25%, but the device structure is relatively complex, and generally requires expensive low-conductivity p-type organic semiconductors as hole transport materials. As a typical semiconductor, it is very important to realize the bipolar doping of methylamine lead iodine (CH3NH3PbI3) that is the light-absorbing layer of perovskite solar cell. Also, it is significant to develop perovskite cells with new device structure. Here, we chose lithium iodide (LiI) as the dopant and successfully grow p-type Li+ doped CH3NH3PbI3 (MAPbI3:Li) perovskite films with low resistivity (103 Ω•cm). The temperature-dependent photoluminescence, Hall effect and Kelvin probe force microscope (KPFM) results strongly confirmed that Li+ doping promotes the transformation of pristine weak n-type MAPbI3 to intentionally doped p-type film. Subsequently, the p-type MAPbI3 film is used as both the light absorption layer and hole transport layer, and form a PN heterojunction with n-type titanium dioxide (TiO2), which is used as the electron transport layer, to construct the heterostructural perovskite cell with a photoelectric conversion efficiency (PCE) of 10.43%. The electron beam induced current (EBIC) signal also strongly confirms the existence of the PN heterojunction and the new working mechanism of such new solar cells.

In Operando, Photovoltaic, and Microscopic Evaluation of Recombination Centers in Halide Perovskite-Based Solar Cells.

The origin of the low densities of electrically active defects in Pb halide perovskite (HaP), a crucial factor for their use in photovoltaics, light emission, and radiation detection, remains a matter of discussion, in part because of the difficulty in determining these densities. Here, we present a powerful approach to assess the defect densities, based on electric field mapping in working HaP-based solar cells. The minority carrier diffusion lengths were deduced from the electric field profile, measured by electron beam-induced current (EBIC). The EBIC method was used earlier to get the first direct evidence for the n-i-p junction structure, at the heart of efficient HaP-based PV cells, and later by us and others for further HaP studies. This manuscript includes EBIC results on illuminated cell cross sections (in operando) at several light intensities to compare optoelectronic characteristics of different cells made by different groups in several laboratories. We then apply a simple, effective single-level defect model that allows deriving the densities (Nr) of the defect acting as recombination center. We find Nr ≈ 1 × 1013 cm-3 for mixed A cation lead bromide-based HaP films and ∼1 × 1014 cm-3 for MAPbBr3(Cl). As EBIC photocurrents are similar at the grain bulk and boundaries, we suggest that the defects are at the interfaces with selective contacts rather than in the HaP film. These results are relevant for photovoltaic devices as the EBIC responses distinguish clearly between high- and low-efficiency devices. The most efficient devices have n-i-p structures with a close-to-intrinsic HaP film, and the selective contacts then dictate the electric field strength throughout the HaP absorber.

Influence of alkali element post-deposition treatment on the performance of the CIGS solar cells on flexible stainless steel substrates

In this study, we studied the effect of different alkali element post-deposition treatment (PDT) on the properties of CuInGaSe2 (CIGS) solar cells deposited on flexible stainless steel (SS) substrate. It is found that a certain amount of Na or K is diffused into the surface layer and inside of the CIGS absorption layer by post-deposition treatment process, which can increase the carrier concentration of the absorption layer and effectively improve the material properties of the absorption layer material, thereby improving the open circuit voltage (VOC) and fill factor (FF) of the device. Electron beam-induced current (EBIC) and Capacitance–voltage (C–V)) measurements indicated that the length of the current collection of CIGS absorption layer treated with NaF PDT and NaF + KF PDT is much larger and the total number of net carrier concentration increases significantly. This phenomenon could be attributed to the increase in carrier lifetime after the PDT treatment.

High-resolution planar electron beam induced current in bulk diodes using high-energy electrons

Understanding the impact of high-energy electron radiation on device characteristics remains critical for the expanding use of semiconductor electronics in space-borne applications and other radiation harsh environments. Here, we report on in situ measurements of high-energy electron radiation effects on the hole diffusion length in low threading dislocation density homoepitaxial bulk n-GaN Schottky diodes using electron beam induced current (EBIC) in high-voltage scanning electron microscopy mode. Despite the large interaction volume in this system, quantitative EBIC imaging is possible due to the sustained collimation of the incident electron beam. This approach enables direct measurement of electron radiation effects without having to thin the specimen. Using a combination of experimental EBIC measurements and Monte Carlo simulations of electron trajectories, we determine a hole diffusion length of 264 ± 11 nm for n-GaN. Irradiation with 200 kV electron beam with an accumulated dose of 24 × 1016 electrons cm−2 led to an approximate 35% decrease in the minority carrier diffusion length.

Geometric effects on carrier collection in core–shell nanowire p–n junctions

We report electron-beam-induced current (EBIC) microscopy carried out on free-standing GaAs nanowire core–shell, p–n tunnel junctions. The carrier kinetics in both the n-type core and the p-type shell were determined by analyzing radial EBIC profiles as a function of beam energy. These profiles are highly sensitive to geometric effects such as facet width, shell and core thicknesses, and depletion widths. Combined with Monte Carlo simulations, they permitted measurement of the minority carrier diffusion lengths in the core and the shell, as well as the depletion widths as a function of radial direction. The relatively short minority carrier diffusion length in the core (50 nm), can be attributed to bulk point defects originating from low-temperature core growth (400 ∘C), or to interfacial recombination at traps at the p–n junction.

Electron‐Beam‐Induced Current and Deep‐Level Transient Spectroscopy Study of Dislocation Trails in Au‐Doped Si

The properties of extended defects introduced by plastic deformation at 600 °C in n‐Si co‐doped with gold are studied by the electron‐beam‐induced current (EBIC) and deep‐level transient spectroscopy (DLTS) methods. It is shown that intrinsic point defects generated by moving dislocations stimulate the gold redistribution. As a result, regions depleted with gold are formed near dense dislocation rows. It is shown that dislocation trails decorated with gold are charged, which is a reason for the formation of bright EBIC contrast outside the Schottky barrier.