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We report on ten-stage interband cascade light-emitting diodes (ICLEDs) using an InAs/GaAsSb superlattices active region with a peak emission wavelength of 4.9 μm at the temperature of 80 K. The ICLED devices integrated with an immersion lens achieve a wall-plug quantum efficiency of 6.6% and an emittance of 1.9 W/cm2 under 80 K and 7.7 A/cm2, which is seven times larger than the basic device without the immersion lens. We present a detailed analysis of the recombination rates and their relationship with the quantum efficiency. The Shockley–Read–Hall and Auger recombination rates were measured using carrier-density dependent time-resolved photoluminescence spectra. The band structure of InAs/GaAsSb superlattices is calculated to study their relationship with the Auger recombination rates.

The integration of single quantum dots (QDs) into a planar Fabry–Perot microcavity has been established as a direct and viable approach to vertically steer photons emitted from the quantum emitters, resulting in a strong increase in the source brightness, which becomes particularly evident when a lens with a low numerical aperture is used. However, the spectral bandwidth of QD–microcavity structures is limited and determined by their intrinsic quality factor; these structures are, thus, not ideal for the extraction of entangled photon pairs or for studies of exciton dynamics. We have found that, when a deterministic low-index solid immersion lens is placed on top of the QD in a QD–microcavity structure, the structure exhibits an enhancement in the bandwidth to 27 nm and a source brightness of 23%. The solid immersion lens is deterministically fabricated via two-photon absorption and can be remade several times without perturbing the QD, ensuring that the QD's intrinsic properties are preserved and ensuring its long-term reliability.

Acoustic waves have been widely applied in communications, medical treatment, military, and other aspects. In this Letter, we explore acoustic imaging properties of three-dimensional Maxwell's fish-eye lens (3D-MFEL) with elevated refractive index profile, the analytical and numerical results show that a 3D-MFEL based on solid immersion mechanism can achieve super-resolution imaging without chromatic aberration. In addition, introducing vortex waves into the 3D-MFEL, we further explore the super-resolution imaging properties in reconstructing vortex waves. The valid combination of 3D-MFEL and solid immersion mechanism provides a meaningful way for super-resolution imaging, which also paves a way forward for future designing and manufacturing in acoustic super-imaging systems.

Unique effects of terahertz (THz)-wave–matter interaction push rapid progress in THz optoelectronics aimed at bridging the problematic THz gap. However, majority of modern methods of THz spectroscopy and imaging are still hampered by low spatial resolution. Common lens/mirror-based THz optics fails to overcome the Abbe barrier and usually provides resolution larger than a free-space wavelength λ (i.e., hundreds of micrometers or even few millimeters). To mitigate this difficulty, supperresolution THz imaging modalities were introduced recently, among which we particularly underline different methods of THz scanning-probe near-field microscopy. They not only rely on strong light confinement on sub-wavelength probes and provide resolution down to [Formula: see text]–[Formula: see text] but also suffer from small energy efficiency or presume an interplay among imaging resolution, signal-to-noise ratio, and performance. In this paper, we consider reflection-mode THz solid immersion (SI) microscopy that offers some compromise between the high imaging resolution of [Formula: see text] and high energy efficiency, which is due to the absence of any subwavelength probe in an optical scheme. Recent achievements, challenging problems, and prospects of SI microscopy are overviewed with an emphasis on resolving the inverse problem and applications in THz biophotonics.

We have developed a method of solid immersion THz imaging—a non-contact technique employing the THz beam focused into evanescent-field volume and allowing strong reduction in the dimensions of THz caustic. We have combined numerical simulations and experimental studies to demonstrate a sub-wavelength 0.35λ0-resolution of the solid immersion THz imaging system compared to 0.85λ0-resolution of a standard imaging system, employing only an aspherical singlet. We have discussed the prospective of using the developed technique in various branches of THz science and technology, namely, for THz measurements of solid-state materials featuring sub-wavelength variations of physical properties, for highly accurate mapping of healthy and pathological tissues in THz medical diagnosis, for detection of sub-wavelength defects in THz non-destructive sensing, and for enhancement of THz nonlinear effects.

A method to control the ion current in direct-current plasma-immersion ion implantation (PIII) is reported for low-pressure magnetized inductively coupled plasma. The ion current can be conveniently adjusted by applying bias voltage to the conducting grid that separates plasma formation and implantation (ion acceleration) zones without the need to alter the rf input power, gas flux, or other operating conditions. The ion current that diminishes with an increase in grid bias in magnetized plasmas can be varied from 48 to 1 mA by increasing the grid voltage from 0 to 70 V at −50 kV sample bias and 0.5 mTorr hydrogen pressure. High implantation voltage and monoenergetic immersion implantation can now be achieved by controlling the ion current without varying the macroscopic plasma parameters. The experimental results and interpretation of the effects are presented in this letter. This technique is very attractive for PIII of planar samples that require on-the-fly adjustment of the implantation current at hig...

The sheath thickness in plasma immersion ion implantation has been investigated in the presence of a transverse magnetic field. It has been found that the steady-state sheath thickness increases with increasing magnetic field strength. This result is in line with a simplified model of the sheath in which the steady-state sheath thickness is determined by the plasma density and ion velocity at the sheath edge. These results suggest that a magnetic field may be used to control the high-voltage sheath in plasma immersion ion implantation.

We report a study of a gallium phosphide, hemispherical, solid immersion lens through the imaging of 40-nm-diam fluorescent dye balls. A spatial resolution as small as 139 nm has been achieved at a wavelength of 560 nm, which is equivalent to a diffraction-limited system of numerical aperture 2.0. This resolution is a 33% improvement over conventional oil immersion objectives and previously reported solid immersion lenses, which typically have a numerical aperture around 1.5.

This letter shows how an aplanatic solid immersion lens system may be used for high-resolution wide-field surface plasmon microscopy. The lens configuration means that no fluid couplant is required; it has the additional advantage that very high refractive indices may be used to reduce the incident angle at which surface plasmons are excited. A transmission spatial light modulator is incorporated conjugate with the back focal plane; this allows the image contrast to be controlled in a precise and flexible manner. Its use also provides definitive demonstration that the image contrast arises from surface plasmon excitation.

The composition of the low-energy ions arising from the rise and fall time periods of the voltage pulse in plasma immersion ion implantation (PIII) are simulated by particle-in-cell (PIC) modeling. It is shown that more than 70% of the low-energy ions with an energy corresponding to less than half of the applied voltage come from the short rise time period. Although the fall time period is typically 30 times longer than the rise time, less than 25% of the low-energy ions originate from it. Based on the PIC results, the depth profile of the implanted ions is derived using the Monte-Carlo code SRIM2000 [J. F. Ziegler, The Stopping and Range of Ions in Solids (Pergamon, New York, 1985)]. The low-energy ions are found to be implanted to a much shallower depth than ions introduced during the fall time period the concentration profile which decays more sharply into the bulk. These results indicate that the most effective way to reduce or increase the surface concentration is by adjusting the rise time of the PIII voltage pulse. This will require a power supply capable of fast rise times and good matching between power supply and load.

The reflected image of a diffraction limited focused spot is investigated using confocal solid immersion microscopy. We find that the spot’s image shows aberrations when reflected off objects with optical indexes lower than that of the solid immersion lens (SIL) material. We demonstrate that such aberrations are only apparent and that the actual size of the spot at the SIL/object interface remains diffraction limited. The aberrations are due to lateral waves at the SIL surface. These von Schmidt waves originate from the total internal reflected components of a diverging spherical wave front. We make use of this image aberration in conjunction with the spatial filtering inherent to confocal microscopy in order to dramatically enhance the optical contrast of objects with low optical indexes.

We report imaging in the infrared with a microfabricated solid immersion lens. The integrated 15-μm-diameter lens and cantilever are fabricated from single-crystal silicon and scanned in contact with a sample to obtain an image. We demonstrate a focused spot size of λ/5 and an effective numerical aperture of 2.5 with λ=9.3 μm light. The total power transmitted through the lens is a factor of 103 greater than through a metal aperture giving the same spatial resolution. Two 1.0 μm holes in a metal film separated by 3.0 μm are imaged with the solid immersion lens in transmission and shown to be resolved.

We show an enhanced spatial resolution using a solid immersion lens by directly imaging the Raman scattered light from silicon masked by periodic metal lines. A glass hemisphere solid immersion lens with an index of refraction n=1.868 at 488 nm is used in conjunction with a 100×0.8 numerical aperture objective to obtain the enhanced spatial resolution. The increased numerical aperture is demonstrated by a direct line scan over the periodic metal lines. Compared with near-field optical microscopy, the solid immersion lens technique overcomes the difficulty of limited excitation power obtainable with tapered fibers, while providing excellent spatial resolution which in principle could be extended to the 0.1 μm range.

In plasma immersion ion implantation, the sample is negatively biased and a plasma sheath forms. Ions are accelerated to the sample surface through this sheath. The electric field contours dictate the shape of the plasma sheath that wraps around corners and tends to be smoother and rounder than the surface topography, for instance, at a sharp corner. Our theoretical and experimental studies reveal ion flux focusing effects leading to lateral nonuniformity of the incident ion dose. Ion focusing occurs not only at the sample edge but also in the central region even for a planar sample (wafer). In this work, we numerically and experimentally investigate this ion focusing effect and ion dose nonuniformity. A simple geometric model is also presented in this letter to understand the mechanism. The results demonstrate that ion focusing originates from plasma sheath convergence that is time and space dependent. Consequently, multiple ion focusing may occur at different local sites when the target shape and processing parameters vary, and a small plasma sheath relative to the target is of paramount importance for uniform implantation.

We present a scanning near-field infrared microscopy technique using transient solid immersion lenses as near-field probes. The transient SILs were formed by photoinducing a zone plate structure on the surfaces of semiconductor wafers with high indices of refraction. Lenses with different number of zones have been tested using gallium phosphide and silicon wafers and their focusing properties were determined. We demonstrate that transient SILs can have lifetimes longer than 50 ps and provide the same high numerical apertures as conventional SILs. The use of transient SILs eliminates the need for mechanical scanning of the lens or sample, thus providing much faster scanning and the possibility to work with soft and liquid objects.

High efficiency of light collection was demonstrated by applying solid immersion lenses (SILs) with refractive indices n=1.845 and 1.687 to fluorescence microscopy of 0.11-μm-radius dye-doped polystyrene sphere beads. This was analyzed with theories on the radiation of dipoles near the surface of the dielectric medium. The estimated collection efficiency with the NA=0.8 objective and the n=1.845 SIL was about 60%–70%, which well exceeds the diffraction-limit value of 50% for 2π-solid angle collection in conventional methods.

Quasi-dc (direct current) plasma immersion ion implantation (PIII) is demonstrated in the long-pulse mode. To prevent plasma extinction as a result of the sheath reaching the vacuum chamber wall in long-pulse experiments, a grounded grid is used to partition the chamber into two halves. The pulse width can be readily increased to 500 μs that is more than 10 times longer than that in typical low-pressure PIII experiments for monoenergetic implantation (ion mean free path≫sheath thickness). The electron saturation current measured by the Langmuir probe indicates that the grounded grid indeed stops the propagation of the plasma sheath. After the plasma sheath reaches the grounded grid, the pulse current drops to a smaller value indicative of the quasi-dc PIII mode. The plasma recovery time is found to be 800 μs thereby limiting the maximum pulsing frequency to below 1 kHz, and the preferred pulse duration window is between 100 and 500 μs. The secondary ion mass spectrometry profiles show that low energy ions...

A method is proposed to prepare ultrathin silicon oxynitride films for gate dielectrics used in deep submicron metal–oxide–semiconductor field effect transistor device structures, namely plasma immersion N implantation into SiO2 films. Plasma immersion implantation pulse voltages in the range 200–1000 V, and fluences from 1016 to 1017 N cm−2 were implanted into thermally grown SiO2 films, with thicknesses between 3 and 6 nm. The areal densities of N and O in the resulting oxynitride films were determined by nuclear reaction analysis, before and after annealing in high-vacuum. N, O, and Si profiles in the films were determined with subnanometric depth resolution by medium energy ion scattering. The results indicate that plasma immersion ion implantation allows for shallow and controlled deposition of significant amounts of nitrogen (up to 3.8 nm of equivalent Si3N4 thickness). Implantation is accompanied by moderate damage at the oxynitride/Si interface which can be recovered by thermal annealing.

Measurements of the ion current collected by a substrate biased to high voltage have been carried out in plasma immersion ion implantation with a filtered vacuum arc plasma source. We have found that the ion saturation current increases with applied voltage and that this effect depends upon the angle of the normal to the substrate with respect to the plasma stream and on the distance of the substrate from the plasma duct exit. We also found that the ion current increases with increasing angle of the normal to the substrate with respect to the plasma stream. A model was developed for the sheath expansion in a nonuniform plasma with substantial ion drift velocity. We find that nonuniformity and high drift velocity lead to a decrease in sheath thickness. In a nonuniform plasma, the ion saturation current increases with applied voltage. The predictions of the model were found to be in good agreement with experiment.

Pump–probe measurements with a subwavelength spatial resolution of 355 nm and a temporal resolution of 130 fs have been performed in a multiple quantum well sample at T=8 K. A solid immersion lens was used to increase the spatial resolution to 0.41⋅λ and the effective numerical aperture to 1.23, demonstrating that the limit of conventional microscopy has been surpassed. The lateral carrier transport was investigated on subpicosecond timescales.

We present an experimental and theoretical study of the immersing properties of a micron-sized solid immersion lens (μ-SIL) and evaluate its capabilities of functioning as a near-field probe. It was found that the μ-SIL reduces an impinging focused spot by a factor of approximately its refractive index, similarly to a macroscopic solid immersion lens. This reduced immersed spot is used to investigate the visibility of a periodic grating structure. Results show an improvement in the visibility by approximately 30% when compared to confocal microscopy, demonstrating the potential application of these tiny micro-lenses as a near-field probe in scanning microscopy and other high-resolution optical systems.

It is suggested that breakdown of a space-charge sheath obeys similar breakdown laws as known for vacuum breakdown. When metal plasmas of vacuum arcs are used, the sheath between a biased substrate and plasma is very thin and the electric-field strength is very high. Field enhancement (e.g., at sharp edges of the substrate) leads to thermal instability of electron emission centers, followed by dense plasma formation which, in turn, electrically short circuits the sheath (breakdown). Theoretical and experimental evidence for this mechanism is presented.

Carrier diffusion and drift in facet-growth quantum wells (QWs) on mesa-patterned substrates by molecular beam epitaxy was studied by high-resolution microscopic photoluminescence spectroscopy and imaging using a solid immersion lens at low temperatures. Under point excitation, excitation-position-dependent anisotropic carrier migration was observed, which was explained by carrier diffusion and drift due to spatial change in the quantization energy in QWs.

A solid immersion lens (SIL) was applied to microscopic photoluminescence (PL) imaging at low temperatures. The spatial resolution corresponding to a numerical aperture of 1.0 was achieved and confirmed to be independent of temperature from 5 to 300 K. We performed PL imaging with the SIL for a GaAs quantum well and obtained stable PL images with high-spatial resolution at a wide temperature range from 5 to 200 K. From the temperature dependence of the PL images with high-spatial resolution, we can directly reveal the diffusion of photocarriers in the sample, which indicates the usefulness of the SIL technique.

Plasma immersion ion implantation has been demonstrated to be a viable technique for microelectronics processing such as fabrication of shallow junction and silicon on insulator. However, a wider acceptance of this fledgling technology by the semiconductor industry is not possible unless the stringent dose and energy uniformity requirements can be met. We have recently discovered that the lateral dose and energy nonuniformity that is unacceptable to the silicon industry stems from the insulating shroud commonly used around the sample stage to reduce the current demand on the power supply. We have developed a theoretical model to explain the experimental results. The model can also be used to optimize the operating conditions and equipment design to achieve the desired dose and energy uniformity across a planar silicon wafer to satisfy the semiconductor industry.

We report a near-field scanning optical microscope using a solid immersion lens having a sharp tip that is mounted to a cantilever. The sharp tip allows the sample to enter the near field of the illumination. The cantilever provides sensitive control of forces. We describe two types of near-field optical contrast, interference and reflection, that simultaneously measure surface topography and reflectivity. Using a super-hemispherical lens with index n=2.2 and 442 nm illumination, the microscope resolves optical features smaller than 150 nm, a factor of 2 improvement over a conventional optical microscope.

We report the implementation of ion-cut silicon-on-insulator (SOI) wafer fabrication technique with plasma immersion ion implantation (PIII). The hydrogen implantation rate, which is independent of the wafer size, is considerably higher than that of conventional implantation. The simple PIII reactor setup and its compatibility with cluster-tools offer other ion-cut process optimization opportunities. The feasibility of the PIII ion-cut process is demonstrated by successful fabrication of SOI structures. The hydrogen plasma can be optimized so that only one ion species is dominant. The feasibility of performing ion-cut using helium PIII is also demonstrated.

A near‐field optical technique, using a new type of solid immersion lens (SIL), has been developed and applied to the writing and reading of domains in magneto‐optic material. The SIL is a truncated glass sphere which serves to increase the numerical aperture of the optical system by n2, where n is the index of refraction of the lens material. Using a SIL made from n=1.83 glass and illuminating with 780 nm light, we have achieved a 317 nm spot size. We have resolved a 500 nm period grating, and written and read 350 nm diameter magnetic domains. The technique should be capable of a 125 nm focused spot size using blue light.

Plasmonic lithography has been used in nanofabrication because of its utility beyond the diffraction limit. The resolution of plasmonic lithography depends on the nano-gap between the nanoaperture and the photoresist surface—changing the gap distance can modulate the line-width of the pattern. In this letter, we demonstrate solid-immersion lens based active non-contact plasmonic lithography, applying a range of gap conditions to modulate the line-width of the pattern. Using a solid-immersion lens-based near-field control system, the nano-gap between the exit surface of the nanoaperture and the media can be actively modulated and maintained to within a few nanometers. The line-widths of the recorded patterns using 15- and 5-nm gaps were 47 and 19.5 nm, respectively, which matched closely the calculated full-width at half-maximum. From these results, we conclude that changing the nano-gap within a solid-immersion lens-based plasmonic head results in varying line-width patterns.

The selective fabrication of ultrashallow p+/n junctions in silicon using projection gas immersion laser doping is reported. The method offers substantial improvement and simplification in junction formation to integrated circuit manufacturers, since several processing steps required for conventional doping techniques like ion implantation are eliminated. Spatially selective incorporation of boron into silicon without the use of any masking layer on the wafer surface is achieved. A pulsed excimer laser beam is patterned using a chromeless reticle and the pattern is transferred through a projection system onto a wafer that is kept in a BF3 dopant gas ambient. The depth of the fabricated junctions is 60 nm with a surface concentration of 5×1019 cm−3. The vertical and lateral distribution of boron in silicon after patterned laser processing is investigated using secondary ion mass spectroscopy (SIMS) and time‐of‐flight SIMS (ToF‐SIMS). Vertical and lateral dopant profiles are steep and clearly resolved.

Selective deposition of copper in SiO2 trenches has been carried out using Pd/Si plasma immersion ion implantation and electroless Cu plating. To form the seed layer for electroless Cu plating on SiO2, sputtered Pd and Si atoms were partially ionized by the Ar plasma and then deposited at bottoms of SiO2 trenches; Ar ion beam was then applied to assist the mixing of the deposited Pd/Si films with the SiO2 substrate by recoil implantation. We found a threshold Pd dose of 2×1014/cm2 is required to initiate the electroless plating of Cu. By careful control of the anisotropic etching of the oxide trenches and proper choice of the Pd dose, 1‐μm wide Cu filled lines with flat surfaces suitable for planarized multilevel metallization were successfully fabricated.

Novel optical components based on metasurfaces (metalenses) offer a new methodology for microlens arrays. In particular, metalens arrays have the potential of being monolithically integrated with infrared focal plane arrays (IR FPAs) to increase the operating temperature and sensitivity of the latter. In this work, we demonstrate a new type of transmissive metalens that focuses the incident light ({\lambda} = 3-5 {\mu}m) on the detector plane after propagating through the substrate, i.e. solid-immersion type of focusing. The metalens is fabricated by etching the backside of the detector substrate material (GaSb here) making this approach compatible with the architecture of back-illuminated FPAs. In addition, our designs work for all incident polarizations. We fabricate a 10x10 metalens array that proves the scalability of this approach for FPAs. In the future, these solid-immersion metalenses arrays will be monolithically integrated with IR FPAs.

Sub‐100 nm P+/N junctions were fabricated using plasma immersion ion implantation (PIII). With this technique, the silicon wafer was immersed in SiF4/BF3 plasma and biased with a negative voltage. The positively charged ions in the plasma sheath were accelerated by the electric field and implanted into the wafer. The dose rate of PIII can be much higher than that of conventional ion implanter. Whereas the dopant activation behavior is similar. For extremely shallow P+/N junction formation, sample preamorphization and short cycle rapid thermal annealing (RTA) are required. With SiF4 PIII preamorphization followed by BF3 PIII doping and RTA at 1060 °C for 1 s, 80 nm P+/N junctions were successfully obtained. Test diodes fabricated with this technique show good characteristics.