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In the present article, we propose a monolithically integrated Michelson interferometer using a λ = 4 µm InGaAs/InAlAs quantum cascade laser as the light source. By using simple fringe detection and a four-point interpolation on each fringe, we will be able to detect minimal object displacements of 500 nm—corresponding to 25% of half the laser emission wavelength. Such an interferometric photonic integrated circuit has interesting applications for precision computerized numerical controlled machines. Since the industrial standard of such machines currently consists of glass-based linear encoders with a resolution of 5 µm, our interferometer-based system will enable an improvement of at least one order of magnitude. [ABSTRACT FROM AUTHOR]

Gallium ion (Ga+) beam damage induced indium (In) precipitation in indium gallium arsenide (InGaAs)/indium aluminium arsenide (InAlAs) multiple quantum wells and its corresponding evolution under electron beam irradiation was investigated by valence electron energy loss spectroscopy (VEELS) and high‐angle annular dark‐field imaging (HAADF) in scanning transmission electron microscopy (STEM). Compared with argon ion milling for sample preparation, the heavier projectiles of Ga+ ions pose a risk to trigger In formation in the form of tiny metallic In clusters. These are shown to be sensitive to electron irradiation and can increase in number and size under the electron beam, deteriorating the structure. Our finding reveals the potential risk of formation of In clusters during focused ion beam (FIB) preparation of InGaAs/InAlAs quantum well samples and their subsequent growth under STEM‐HAADF imaging, where initially invisible In clusters of a few atoms can move and swell during electron beam exposure. LAY DESCRIPTION: In this paper, the evolution of Ga+ implantation induced In precipitation in InGaAs/InAlAs multiple quantum wells under electron beam irradiation was investigated by valence electron energy loss spectroscopy (VEELs), energy dispersive X‐ray spectroscopy (EDXs) and high‐angle annular dark‐field (HAADF) imaging technique based in a probe aberration corrected scanning transmission electron microscope. In contrast to Ar+ ion bombardment, the projectile of focused Ga+ ions is able to trigger the clustering of In interstitials in InGaAs/InAlAs multiple quantum wells, which allows the formation of metallic In precipitates. Afterwards, by exploiting an extensive electron beam rastering on the region of In precipitation, the increase of electron irradiation time could lead to a pronounced swelling of In cluster size. Especially for the region contains In precipitates of several atoms, where the morphology of In cluster is invisible in atomic image. The continuous electron irradiation could give rise to the promotion of In clustering, allowing the structure of In precipitates been resolved by HAADF image. Our finding reveals the potential risk of formation of In precipitates during focused Ga+ ion beam bombarded InGaAs/InAlAs semiconductors and the subsequent evolution of In clustering under electron beam rastering. These findings emphasise the need for caution when studying FIB prepared In‐based III–V quantum well specimens using TEM even in the In(Ga,Al)As system, as the initially formed In‐rich clusters are so small they can remain invisible for some time. [ABSTRACT FROM AUTHOR]

In the present article, we propose a monolithically integrated Michelson interferometer using a λ = 4 µm InGaAs/InAlAs quantum cascade laser as the light source. By using simple fringe detection and a four-point interpolation on each fringe, we will be able to detect minimal object displacements of 500 nm—corresponding to 25% of half the laser emission wavelength. Such an interferometric photonic integrated circuit has interesting applications for precision computerized numerical controlled machines. Since the industrial standard of such machines currently consists of glass-based linear encoders with a resolution of 5 µm, our interferometer-based system will enable an improvement of at least one order of magnitude.

To give consideration to both chip density and device performance, an In0.53Ga0.47As vertical electron–hole bilayer tunnel field effect transistor (EHBTFET) with a P+-pocket and an In0.52Al0.48As-block (VPB-EHBTFET) is introduced and systematically studied by TCAD simulation. The introduction of the P+-pocket can reduce the line tunneling distance, thereby enhancing the on-state current. This can also effectively address the challenge of forming a hole inversion layer in an undoped InGaAs channel during device fabrication. Moreover, the point tunneling can be significantly suppressed by the In0.52Al0.48As-block, resulting in a substantial decrease in the off-state current. By optimizing the width and doping concentration of the P+-pocket as well as the length and width of the In0.52Al0.48As-block, VPB-EHBTFET can obtain an off-state current of 1.83 × 10−19 A/μm, on-state current of 1.04 × 10−4 A/μm, and an average subthreshold swing of 5.5 mV/dec. Compared with traditional InGaAs vertical EHBTFET, the proposed VPB-EHBTFET has a three orders of magnitude decrease in the off-state current, about six times increase in the on-state current, 81.8% reduction in the average subthreshold swing, and stronger inhibitory ability on the drain-induced barrier-lowering effect (7.5 mV/V); these benefits enhance the practical application of EHBTFETs. [ABSTRACT FROM AUTHOR]

To give consideration to both chip density and device performance, an In0.53Ga0.47As vertical electron–hole bilayer tunnel field effect transistor (EHBTFET) with a P+-pocket and an In0.52Al0.48As-block (VPB-EHBTFET) is introduced and systematically studied by TCAD simulation. The introduction of the P+-pocket can reduce the line tunneling distance, thereby enhancing the on-state current. This can also effectively address the challenge of forming a hole inversion layer in an undoped InGaAs channel during device fabrication. Moreover, the point tunneling can be significantly suppressed by the In0.52Al0.48As-block, resulting in a substantial decrease in the off-state current. By optimizing the width and doping concentration of the P+-pocket as well as the length and width of the In0.52Al0.48As-block, VPB-EHBTFET can obtain an off-state current of 1.83 × 10−19 A/μm, on-state current of 1.04 × 10−4 A/μm, and an average subthreshold swing of 5.5 mV/dec. Compared with traditional InGaAs vertical EHBTFET, the proposed VPB-EHBTFET has a three orders of magnitude decrease in the off-state current, about six times increase in the on-state current, 81.8% reduction in the average subthreshold swing, and stronger inhibitory ability on the drain-induced barrier-lowering effect (7.5 mV/V); these benefits enhance the practical application of EHBTFETs.

AbstractWe calculated the correlation between the doping concentration of the charge layer and the multiplication layer for separate absorption, grading, charge, and multiplication InGaAs/InAlAs avalanche photodiodes (APDs). For this purpose, a predictable program was developed according to the concentration and thickness of the charge layer and the multiplication layer. We also optimized the design, fabrication, and characteristics of an APD for 20 Gbps application. The punch‐through voltage and breakdown voltage of the fabricated device were 10 V and 33 V, respectively, and it was confirmed that these almost matched the designed values. The 3‐dB bandwidth of the APD was 10.4 GHz, and the bit rate was approximately 20.8 Gbps.

—We constructed a model for a 3-stage InGaAs/InAlAs avalanche photodiode using numerical simulations based on the gain-noise mechanism. The contact layer, barrier layer, charge layer and multiplication layer of this model are optimized accordingly. The performance of the device can be improved by optimizing the thickness and doping concentration of the contact layer, increasing the thickness of the charge layer, and adding a barrier layer. At the same time, the addition of double heterojunction structure makes the performance of the device better, which enables a higher impact ionization rate of the multiplication layer. According to DSMT theory calculation results, the optimized 3-gain-stage device's gain is 90, and the excess noise factor is about 3.1. Compared with the 10-stage avalanche photodiode (with an excess noise factor of 5) studied at the same gain, this work shows higher performance at the lower stage. The optimized structure can provide design and optimization ideas for more stages of avalanche photodiode to increase gain and reduce excess noise. [ABSTRACT FROM AUTHOR]

A $15~\mu \text{m}$ pitch extended wavelength In0.83Ga0.17As/ InP mega-pixel focal plane array (FPA) with a format of 1280 $\times 1024$ and a spectral response range of 1150–2450 nm has been demonstrated for the first time. High fill factor up to >86%, low dark current densities down to < 133 nA/cm2, high quantum efficiencies up to >69%, were achieved by implementing novel high density micro-mesa array processing technologies. A proprietary wafer bowing control technique was developed, attaining a high pixel operability of 99.37%. Laboratory imaging was also demonstrated, showing potentiality for high resolution imaging applications in a wider SWIR spectrum range. [ABSTRACT FROM AUTHOR]

We calculated the correlation between the doping concentration of the charge layer and the multiplication layer for separate absorption, grading, charge, and multiplication InGaAs/InAlAs avalanche photodiodes (APDs). For this purpose, a predictable program was developed according to the concentration and thickness of the charge layer and the multiplication layer. We also optimized the design, fabrication, and characteristics of an APD for 20 Gbps application. The punch‐through voltage and breakdown voltage of the fabricated device were 10 V and 33 V, respectively, and it was confirmed that these almost matched the designed values. The 3‐dB bandwidth of the APD was 10.4 GHz, and the bit rate was approximately 20.8 Gbps. [ABSTRACT FROM AUTHOR]

A highly sensitive terahertz (THz) detector based on a photoconductive antenna (PCA) with plasmonic amplification on the basis of an InGaAs/InAlAs superlattice heterostructure is proposed. A noticeable increase in the photocurrent recorded by a plasmonic PCA detector and the signal-to-noise ratio was experimentally detected compared to the same parameters for the PCA detector without plasmonic electrodes. The efficiency of plasmonic electrodes has been experimentally confirmed by pulsed THz spectroscopy by measuring the dependence of the detector's THz signal amplitude on the polarization of the incident pump laser radiation. [ABSTRACT FROM AUTHOR]

An optimized empirical modelling for a 0.25µm gate length of highly strained channel of an InP-based pseudomorphic high electron mobility transistor (pHEMT) using InGaAs-InAlAs material systems is presented. An accurate procedure for extraction is described and tested using the pHEMT measured dataset of I-V characteristics and related multi-bias s-parameters over 20GHz frequency range. The extraction of linear and nonlinear parameters from the small signal and large signal pHEMT equivalent model are performed in ADS. The optimized DC and S-parameter model for the pHEMT device provides a basis for active device selection in the MMIC low noise amplifier circuit designs. [ABSTRACT FROM AUTHOR]

In $$_{x}$$ Ga $$_{1-{x}}$$ As/In $$_{y}$$ Al $$_{1-{y}}$$ As HEMT structures $${\updelta }$$ -doped by Si were grown by molecular beam epitaxy on InP substrate. We investigated the influence of the In content on the electron mobilities and effective masses in dimensionally quantized subbands. The electron effective masses were determined by the temperature dependence of the amplitude of the Shubnikov-de Haas effect at 1.6 and 4.2 K. We found that the more the In content in quantum well (QW), the less the electron effective masses. The mobilities are higher in HEMT structures with wider and deeper QW. The energy band diagrams were calculated by using Vegard's law for basic parameters. The calculated band diagrams are in a good agreement with the experimental data of photoluminescence spectra. [ABSTRACT FROM AUTHOR]

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Abstract: We report the thermal analysis of short wavelength strain-compensated In x Ga1− x As/InyAl1−yAs quantum cascade lasers (QCLs) operating at λ ∼3.8–4.3μm by a two-dimensional heat transfer model using heat source densities obtained from experimental measurements in continuous-wave mode. The heat fluxes and temperature profiles are analyzed for various QCL structures with different bonding schemes, extracting thermal conductance (G th). The use of buried heterostructure (BH) enhances the lateral heat dissipation from the active core region of QCLs. The heatsinking structure in epilayer-down configuration using diamond submount exhibits high G th values with less temperature dependence. For epilayer-down bonded single ridge waveguide 11μm wide and 4mm long BH QCLs at λ ∼3.8μm and λ ∼4.3μm on diamond submount, the improved G th values of 292W/Kcm2 and 409W/Kcm2 at 298K are obtained, respectively. The highly strained InGaAs/InAlAs structure gives a low G th value due to the reduced thermal conductivity. The theoretically calculated results are compared with the existing G th data obtained experimentally, thus showing a good agreement. [Copyright &y& Elsevier]

An extremely high maximum transconductance gm max of 2.25 S/mm and a cutoff frequency ƒT of 310 GHz was achieved at a cryogenic temperature (16 K) in a 195-nm-gate In0.75Ga0.25As/In0.52Al0.48As high electron mobility transistor (HEMT) fabricated on a (411)A-oriented InP substrate by molecular beam epitaxy, compared with room temperature values (fro max = 1.78 S/mm and ƒT = 245 GHz). These significantly enhanced gm max and ƒT values are attributed to a high electron velocity of up to 4.9 × 107 cm/s due to suppressing phonon scattering in the In0.75Ga0.25As/In0.52Al0.48As HEMT with (411)A super-flat InGaAs/InAlAs interfaces (effectively atomically flat heterointerfaces over a wafer-size area). [ABSTRACT FROM AUTHOR]

Abstract: Microwave photoconductivity measurements of InGaAs/InAlAs and GaAs/AlGaAs heterostructures were carried out to investigate electronic spin states. In far-infrared magneto-optical absorption measurement, we confirmed a zero-field spin-splitting energy of the InGaAs/InAlAs heterostructure is 9meV. In microwave modulated photoconductivity measurements, Shubnikov–de Haas oscillation was observed with quite high sensitivity. The energy of the sample was also determined from the oscillation. A dip structure was observed near cyclotron resonance field. By comparing with the result in GaAs/AlGaAs heterostructures and considering the heating effect by microwave irradiation, the origin of the Shubnikov–de Haas-type oscillation and the appearing dip structure are discussed. [Copyright &y& Elsevier]

We achieved a maximum transconductance (gm) of 2.25 S/mm at 16 K for a 195-nm-gate In0.75Ga0.25As/In0.52Al0.48As pseudomorphic high-electron mobility transistor (PHEMT) fabricated on a (411)A-oriented InP substrate, which is the highest value ever reported for HEMTs. This PHEMT also showed a much enhanced cutoff frequency (fT) of 310 GHz at 16 K, compared with its room temperature value (245 GHz). The significantly enhanced gm and fT at 16 K can be attributed to the higher saturation velocity in the region ‘under the gate,’ which is caused not only by suppressing the phonon scattering, but also by suppressing the interface roughness scattering due to the ‘(411)A super-flat InGaAs/InAIAs interfaces’ (effectively atomically flat heterointerfaces over a wafer-size area). [ABSTRACT FROM AUTHOR]

Amplitude modulators are basic devices for long distance optical communication. Their development started using the electro-absorption of bulk material, called the Franz–Keldysh effect. High frequency applications required larger absorption changes with electric field, therefore, attention has been shifted to multiple quantum well structures where the quantum confined Stark effect (QCSE) could improve device performance at high bit rates. However, if the amplitude modulators based on the QCSE are expected to be used in the next multigigabit long-haul fiber transmission systems, the multiple quantum well structure should be optimized taking into consideration parameters such as insertion loss, contrast ratio, chirp, polarization independence, operation voltage and wavelength. Much work has been done in several III–V semiconductor systems. The results of a detailed optimization for InGaAs/InAlAs multiple quantum well structures are presented, as an example. [Copyright &y& Elsevier]

InGaAs/InAlAs double-doped double-strained modulation-doped field-effect transistors OD-SMODFETs)1 were grown by solid source molecular beam epitaxy. The structures were characterized using high resolution x-ray diffraction, Hall effect, and cross-sectional scanning tunneling microscopy. A record two-dimensional electron gas (2DEG) sheet density of 8.5 × 1012/cm2 and 8.1 × 1012/cm2 for 300 and 77K, respectively, was achieved. The mobility was 6500 and 12000 cm2/ Vs for 300 and 77K, respectively. To the author’s knowledge,2 the previous record 2DEG result was 6.58 × 1012/cm2. The electron mobility was limited by alloy scattering and interface roughness caused by the presence of “clustering.” Using cross-sectional scanning tunneling microscopy to verify the presence of these clusters, we have the first images of the lattice matched InAlAs (spacer)-InGaAs (quantum well) interface. These images reveal clusters that have approximate spherical or cylindrical shapes with equivalent cubic dimensions ranging from 25 to 45Å. [ABSTRACT FROM AUTHOR]

InP-based InGaAs/InAlAs ridge quantum wires were successfully fabricated by our new approach using selective molecular beam epitaxy (MBE). As the starting structures, array of InGaAs ridge structures composed of smooth (311)A facets were formed by MBE on mesa-patterned InP substrates. Prior to actual fabrication of the wires, MBE growth characteristics of InGaAs and InAlAs layers on the starting structure were studied in detail. The results of growth experiments were then successfully applied to the fabrication of InGaAs ridge quantum wires with high spatial uniformity. Low temperature cathodoluminescence spectrum measured in response to spot excitation of wire region showed a strong light emission whose analysis indicated that it originates from InGaAs ridge quantum wire itself. In photoluminescence measurements, the emission from the wire had strong intensity even at room temperature, indicating that the wire crystal possesses excellent bulk and interface quality, and are largely free from nonradiative recombination centers. [ABSTRACT FROM AUTHOR]

The effect of structural parameters on the transport characteristics from 15 to 300 K of molecular beam epitaxy-grown InGaAs/InAlAs two dimensional electron gas structures lattice-matched to InP is determined. The InAlAs buffer layer thickness was varied from 1000 to 10,000Å. One sample also incorporated a InGaAs/InAlAs superlattice. The buffer layer thickness and structure had almost no effect on the mobility or sheet density. The InAlAs spacer layer was varied from 25 to 200Å. Increases in the InAlAs spacer thickness resulted in a monotonically decreasing sheet density and a peak in the mobility versus spacer thickness at 100Å. The highest 77 K mobility was 66,700 cm/V/sds with N =1.2×10 cm. The effect of illumination and temperature on the sheet concentration in these structures as well as on 'bulk' InAlAs:Si was much smaller than in AlGaAs/GaAs structures or 'bulk' AlGaAs, for x≅0.30, indicating that devices based on this material system will not be characterized by many of the device instabilities observed in the AlGaAs/GaAs system. [ABSTRACT FROM AUTHOR]

The direct epitaxial growth of ultrahigh-mobility InGaAs/InAlAs quantum-well (QW) device layers onto silicon substrates using metamorphic buffer layers is demonstrated for the first time. In this letter, 80 nm physical gate length depletion- mode InGaAs QW transistors with saturated transconductance gm of 930 µS/µm and fT of 260 GHz at VDS = 0.5 V are achieved on 3.2 µm thick buffers. We expect that compound semiconductor-based advanced QW transistors could become available in the future as very high-speed and ultralow-power device technology for heterogeneous integration with the mainstream silicon CMOS. [ABSTRACT FROM AUTHOR]

We have studied the Rashba constant values α in the In0.52Al0.48As/In0.53Ga0.47As quantum wells (QW), as a function of the degree of the structural inversion asymmetry (SIA), using the weak antilocalization analysis. We control the SIA of the QWs both by the specific sample design and by the applied gate voltage. The deduced α values are in a quantitative agreement with the theoretical values obtained in the k·p-type calculation. We, then, propose a novel spin-filter device solely based on the Rashba effect as an example of the devices that utilize the Rashba spin–orbit coupling effect. [Copyright &y& Elsevier]