InP Barrier Research Articles

Mode competition in a dual-mode quantum-dot semiconductor microlaser

This paper describes the modeling of quantum-dot lasers with the aim of assessing the conditions for stable cw dual-mode operation when the mode separation lies in the THz range. Several possible models suited for InAs quantum dots in InP barriers are analytically evaluated, in particular quantum dots electrically coupled through a direct exchange of excitation by the wetting layer or quantum dots optically coupled through the homogeneous broadening of their optical gain. A stable dual-mode regime is shown possible in all cases when quantum dots are used as active layer whereas a gain medium of quantum well or bulk type inevitably leads to bistable behavior. The choice of a quantum-dot gain medium perfectly matched the production of dual-mode lasers devoted to THz generation by photomixing.

Conductance Enhancement of InAs/InP Heterostructure Nanowires by Surface Functionalization with Oligo(phenylene vinylene)s

We have investigated the electronic transport through 3 μm long, 45 nm diameter InAs nanowires comprising a 5 nm long InP segment as electronic barrier. After assembly of 12 nm long oligo(phenylene vinylene) derivative molecules onto these InAs/InP nanowires, we observed a pronounced, nonlinear I-V characteristic with significantly increased currents of up to 1 μA at 1 V bias, for a back-gate voltage of 3 V. As supported by our model calculations based on a nonequilibrium Green Function approach, we attribute this effect to charge transport through those surface-bound molecules, which electrically bridge both InAs regions across the embedded InP barrier.

A High Performance In0.7Ga0.3As MOSFET with an InP Barrier Layer for Radio-Frequency Application

We demonstrate a high performance implant-free n-type In0.7Ga0.3As channel MOSFET with a 4-nm InP barrier layer fabricated on a semi-insulating substrate employing a 10-nm Al2O3 as gate dielectric. The maximum effective channel mobility is 1862 cm2/V·s extracted by the split C—V method. Devices with 0.8 μm gate length exhibit a peak extrinsic transconductance of 85 mS/mm and a drive current of more than 200 mA/mm. A short-circuit current gain cutoff frequency fT of 24.5 GHz and a maximum oscillation frequency fmax of 54 GHz are achieved for the 0.8 μm gate-length device. The research is helpful to obtain higher performance In0.7Ga0.3As MOSFETs for radio-frequency applications.

Total Ionizing Dose Radiation Effects in Al$_{2}$O$_{3}$-Gated Ultra-Thin Body In$_{0.7}$Ga$_{0.3}$As MOSFETs

We have investigated total ionizing dose (TID) radiation effects in Al <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> O <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> -gated ultra-thin body In <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{0.7}$</tex></formula> Ga <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{0.3}$</tex></formula> As MOSFETs. A non-monotonic dependence of the threshold voltage <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$(V_{\rm th})$</tex></formula> on the X-ray radiation dose was observed and analyzed; the accompanying degradation in subthreshold swing (SS) likely is caused by non-uniform trapped charge in the near-interfacial Al <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> O <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> rather than interface-trap generation. The off-current and gate breakdown voltage were independent of dose up to 6 Mrad(SiO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex> </formula> ). Compared to the InP-free device, the device with an InP barrier is more vulnerable to TID effects in terms of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$V_{\rm th}$</tex></formula> shift, SS, and mobility degradation.

Electronic structure and optical properties of 1.55 µm emitting InAs/InGaAsP quantum dash tunnel injection structures

Optical spectroscopy studies have been reported on an application-relevant system emitting at 1.55 µm and consisting of an InGaAsP injector quantum well (QW), separated by a thin InP barrier (of various thicknesses) from InAs elongated quantum dots called quantum dashes (QDash). The investigated systems constitute tunnel injection structures, whose operation principle is the transfer of carriers captured by the injector QW to the QDash layer by means of tunnelling. Numerical calculations in the eight-band kp model with a realistic dash geometry are used in order to determine the energies of confined levels and their wave functions, results of which are then verified by comparison with measured photoreflectance spectra and used to interpret spectroscopic findings. The tunnelling of carriers from QW to QDash layer is evidenced by photoluminescence excitation measurements and further supported by unusual temperature behaviour of PL peaks broadenings. Careful numerical analysis of confined states and their wave functions explains optical properties of investigated samples. The suggestions for the proper design of structures based on the injection of carriers for applications in telecom lasers are given; most importantly it is shown that care must be taken so that the QW does not significantly influence the dash emitter.

Band alignment and quantum states of InAsxP1−x/InP surface quantum wells investigated from ultraviolet photoelectron spectroscopy and photoluminescence

The band alignment and the quantum states of InAsxP1−x/InP surface quantum well (SQW) are investigated using ultraviolet photoelectron spectroscopy (UPS) and photoluminescence techniques. The analysis of UPS spectra of core levels In 4d, As 3d, P 3p and P 2p confirms that the top surface of InAsxP1−x/InP SQW contains an admixture of oxides, which convert into a more stable form of oxide, In(PO3)3, after optimum Ar+ ion sputtering. The values of valence band offsets between In(PO3)3/InP and InAsxP1−x/InP (x=0.57) SQW are 2.1eV and 0.3eV respectively, as obtained from the onsets of UPS spectra. Further, the band structure of InAsxP1−x/InP SQW is also estimated from the UPS spectra of core levels and the valence band onsets after optimum Ar+ ion sputtering. The emission of the quantum states (e1–hh1) transition blue-shifts by about 60meV for InAs0.38P0.62/InP SQW when the top InP barrier layer thickness is decreased from 22Å to 11Å. The experimental values of e1–hh1 electronic transition in SQW match well with those of the theoretically calculated ones using a 3.6eV potential barrier at the InP surface.

Errors Limiting Split-$CV$ Mobility Extraction Accuracy in Buried-Channel InGaAs MOSFETs

The accuracy of the split- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CV</i> mobility extraction method is analyzed in buried-channel InGaAs MOSFETs with a Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> gate dielectric and an InP barrier, through a “simulated experiment” procedure using 2-D numerical device simulations that are preliminarily calibrated against experimental <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CV</i> curves. The different error sources limiting the method accuracy are pointed out. It is suggested that, as a result of these errors, the split- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CV</i> method can appreciably underestimate the actual channel mobility in these devices, with an error of >;20% and >;50% on peak mobility and high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> mobility, respectively. The method should therefore not be adopted for accurate mobility measurement in this operating regime but only as a fast response technique providing a conservative estimation of channel mobility. Moreover, the method provides mobility values that rapidly drop below the peak value for decreasing <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> . It is shown that this behavior can be an artifact of the extraction method, which may mask physical mechanisms causing a real mobility drop with decreasing channel carrier density, such as Coulomb scattering mechanisms. This poses limitations to the adoption of split- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CV</i> mobility as a reference for mobility model assessment in this operating regime. The proposed methodology can be applied to other III-V FETs, including both heterostructure-based and inversion-mode devices.

Analysis of effective mobility and hall effect mobility in high-k based In0.75Ga0.25As metal-oxide-semiconductor high-electron-mobility transistors

We report an In0.75Ga0.25As metal-oxide-semiconductor high-electron-mobility transistor with a peak Hall mobility of 8300 cm2/Vs at a carrier density of 2 × 1012 cm−2. Comparison of split capacitance-voltage (CV) and Hall Effect measurements for the extracted electron mobility have shown that the split-CV can lead to an overestimation of the channel carrier concentration and a corresponding underestimation of electron mobility. An analysis of the electron density dependence versus gate voltage allows quantifying the inaccuracy of the split-CV technique. Finally, the analysis supported by multi-channel conduction simulations indicates presence of carriers spill over into the top InP barrier layer at high gate voltages.

Mechanisms of molecular beam epitaxy growth in InAs/InP nanowire heterostructures

InAs/InP axial nanowire heterostructures were grown by the Au-assistedvapour–liquid–solid method in a gas source molecular beam epitaxy system. Thenanowire crystal structure and morphology were investigated by transmissionelectron microscopy for various growth conditions (temperature, growth rate,V/III flux ratio). Growth mechanisms were inferred from the InAs and InP segment lengths as afunction of the nanowire diameter. Short InAs segment lengths were found to grow bydepletion of In from the Au particle as well as by direct impingement, while longersegments of InAs and InP grew by diffusive transport of adatoms from the nanowiresidewalls. The present study offers a way to control the lengths of InAs quantum dotsembedded in InP barriers.

High-k InGaAs metal-oxide-semiconductor field-effect-transistors with various barrier layer materials

Improved device performance of InGaAs channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) has been achieved by utilizing InP and InAlAs barrier layer. In0.7Ga0.3As buried-channel MOSFETs with various InP barrier thicknesses and InP/InAlAs double barrier have been fabricated and compared in terms of performances parameters such as drive current, transconductance, subthreshold swing (SS), and effective mobility. Devices with 1 nm InP barrier exhibits 59% increase in drive current and 65% increase in peak effective channel mobility compared to devices without barrier layer. With thicker barrier, devices show higher drive current and higher mobility. Devices with InP/InAlAs double barrier exhibit the highest effective channel mobility.

On the mechanisms limiting mobility in InP/InGaAs buried channel nMISFETs

MISFETs incorporating the InP/InGaAs buried channel showed a high peak mobility of 5500 cm 2/V s. Spillover of the inversion carriers from the buried channel to the MIS interface on the InP barrier layer caused drastic mobility degradation as the carrier concentration was increased. The spillover was evidenced by observing a negative transconductance and a kink in split capacitance–voltage curves. Remote scattering by the trapped charges at the MIS interface also reduced the mobility when the InP barrier layer was as thin as 2 nm.

Temperature dependence of active photonic band gap in bragg-spaced quantum wells

A novel all-optical polarization switch of active photonic band gap structure based on non-resonant optical Stark effect bragg-spaced quantum wells was investigated and it could be compatible with the optical communication system. The theory is based on InGaAsP/InP Bragg-spaced quantum wells (BSQWs). Mainly through the design of the InGaAsP well layer component and InP barrier thickness to make the quantum-period cycle meet the bragg condition and the bragg frequency is equal to re-hole exciton resonance frequency. When a spectrally narrow control pulse is tuned within the forbidden gap, such BSQWs have been shown to exhibit large optical nonlinearities and ps recovery times, which can form T hz switch. However, the exciton binding energy of InGaAsP will be automatically separate at room temperature, so the effect of all-optical polarization switching of active photonic band gap bragg structure quantum wells can only be studied at low temperature. By a large number of experiments, we tested part of the material parameters of BSQWs in the temperature range 10-300K. On this basis, the InGaAsP and InP refractive index changes with wavelength, InP thermal expansion coefficient are studied and a relationship equation is established. Experimental results show that the bragg reflection spectra with temperature mainly is effected by InP refractive index changes with temperature. Our theoretical study and experiment are an instruction as a reference in the designs and experiments of future practical optical switches.

Radiation effects and interphase interactions in ohmic and barrier contacts to indium phosphide as induced by rapid thermal annealing and irradiation with γ-ray 60Co photons

The radiation resistance of Au-Pd-Ti-Pd-n ++-InP ohmic contacts and Au-TiB x -n-n +-n ++-InP barrier contacts—both initial and subjected to a rapid thermal annealing and irradiated with 60Co γ-ray photons with doses as high as 109 R—has been studied. Before and after external effects, the electrical characteristics of the barrier and ohmic contacts, distribution profiles for components, and phase composition in the metallization layers have been measured. In ohmic Pd-Ti-Pd-Au contacts subjected to rapid thermal annealing and irradiation, a significant distortion of the layered structure of metallization occurs; this distortion is caused by the thermal and irradiation-stimulated transport of Pd over the grain boundaries in polycrystalline Ti and Au films. However, the specific contact resistance ρ c does not change appreciably, which is related to a comparatively unvaried composition of the contact-forming layer at the Pd-n +-InP interface. In the initial sample and the sample subjected to the rapid thermal annealing at T = 400°C with the Au-TiB x -n-n +-n ++-InP barrier contacts and irradiated with the dose as high as 2 × 108 R, a layered structure of metallization is retained. After irradiation with the dose as high as 109 R, in the samples subjected to a rapid thermal annealing at T = 400°C, the layered structure of metallization becomes completely distorted; however, this structure is retained in the initial sample. The electrical properties of the contact structure appreciably degrade only after irradiation of the sample preliminarily subjected to a rapid thermal annealing at T = 400°C.

High Performance InGaAs MOSFETs with High Mobility Using InP Barrier Layer

not Available.

How to use a nanowire to measure vibrational frequencies: Device simulator results

Here we present a theoretical investigation of double well nanowire device that will be studied experimentally over a range of temperatures. Our nanowires are made from InAs with three InP barriers between which lie two InAs quantum wells. These wells have associated with them sharp electronic states between which electrons can tunnel. In the absence of a bias, resonant transmission of electrons is possible; but on applying a bias the levels in neighboring wells acquire different energies, thereby frustrating transmission. If the offset in energy is matched by the frequency of a phonon within the device that couples to the electrons in the wells then there will be a rise in current. We present here the results of simple device simulator calculations, on the basis of which the dimensions of an optimized device are determined.

Effects of barrier layers on device performance of high mobility In0.7Ga0.3As metal-oxide-semiconductor field-effect-transistors

We have applied single InP barrier layer with different thicknesses and InP/In0.52Al0.48As double-barrier layer to In0.7Ga0.3As Al2O3 metal-oxide-semiconductor field-effect-transistors (MOSFETs) and investigated their effects on device performance. In0.7Ga0.3As MOSFETs with 3 nm InP single-barrier attain 22% higher peak effective mobility while devices with 5 nm InP attain 58% higher peak mobility than the ones without barrier. Devices using InP/In0.52Al0.48As double-barrier achieve mobility enhancement at both low-field (68% at peak mobility) and high-field (55%) compared to ones without barrier. High channel mobility of 4729 cm2/V s has been obtained using InP/In0.52Al0.48As barrier and atomic-layer-deposited Al2O3 gate oxide.

High Performance InGaAs MOSFETs with High Mobility using InP Barrier Layer

We have fabricated In0.7Ga0.3As and In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors (MOSFETs) with and without InP barrier layer using atomic layer deposited (ALD) Al2O3 gate oxide directly on III-V substrates. InP is an excellent barrier and passivation layer to enhance current driving capability for these devices, especially for In0.7Ga0.3As MOSFETs due to good conduction band offsets. In0.7Ga0.3As MOSFETs with InP barrier layer show much higher transconductance and lower subthreshold swing than other MOSFETs in our study, and exhibit high drive current of 98 mA/mm (L=20 um), subthreshold swing of 106 mV/dec and maximum effective channel mobility of 4402 cm2/Vs, which is amongst the highest reported in the literature.

High Performance InGaAs MOSFETs with High Mobility using InP Barrier Layer

not Available.

High performance In0.7Ga0.3As metal-oxide-semiconductor transistors with mobility &amp;gt;4400 cm2/V s using InP barrier layer

We have investigated device performance for In0.7Ga0.3As and In0.53Ga0.47As metal-oxide-semiconductor transistors (MOSFETs) with and without InP barrier layer using atomic layer deposited Al2O3 gate dielectric. InP barrier layer was found to provide higher transconductance for both In0.7Ga0.3As and In0.53Ga0.47As MOSFETs, especially for In0.7Ga0.3As. In0.7Ga0.3As MOSFETs with InP barrier layer show much higher transconductance and lower subthreshold swing than other MOSFETs studied. These In0.7Ga0.3As MOSFETs exhibit high drive current of 98 mA/mm (L=20 μm), subthreshold swing of 106 mV/decade and maximum effective channel mobility of 4402 cm2/V s.

InP‐quantum dots in Al0.20Ga0.80InP with different barrier configurations

AbstractSystematic ensemble photoluminescence studies have been performed on type‐I InP‐quantum dots in Al0.20Ga0.80InP barriers, emitting at approximately 1.85 eV at 5 K. The influence of different barrier configurations as well as the incorporation of additional tunnel barriers on the optical properties has been investigated. The confinement energy between the dot barrier and the surrounding barrier layers, which is the sum of the band discontinuities for the valence and the conduction bands, was chosen to be approximately 190 meV by using Al0.50Ga0.50InP. In combination with 2 nm thick AlInP tunnel barriers, the internal quantum efficiency of these barrier configurations can be increased by up to a factor of 20 at elevated temperatures with respect to quantum dots without such layers. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)