Stark-effect scattering in rough quantum wells

Jana, Raj K.; Jena, Debdeep

doi:10.1063/1.3607485

Cited by 17 publications

(8 citation statements)

References 12 publications

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“…Since in our samples only the statistical properties of ∆( r) are of importance, we chose for the fluctuation correlation ∆( r)∆(0) = ∆ 2 exp(−r 2 /Λ 2 ) with the correlation length Λ as outlined in Prange et al [64]. With this correlation and the Fourier transform of the integral, the random potential then results in [62] |U int (q)…”

Section: Remaining Scattering Mechanismsmentioning

confidence: 99%

Limiting scattering processes in high-mobility InSb quantum wells grown on GaSb buffer systems

Lehner

Tschirky

Ihn

et al. 2018

Phys. Rev. Materials

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We present molecular beam epitaxial grown single-and double-side δ-doped InAlSb/InSb quantum wells with varying distances down to 50 nm to the surface on GaSb metamorphic buffers. We analyze the surface morphology as well as the impact of the crystalline quality on the electron transport. Comparing growth on GaSb and GaAs substrates indicates that the structural integrity of our InSb quantum wells is solely determined by the growth conditions at the GaSb/InAlSb transition and the InAlSb barrier growth. The two-dimensional electron gas samples show high mobilities of up to 349 000 cm 2 /Vs at cryogenic temperatures and 58 000 cm 2 /Vs at room temperature. With the calculated Dingle ratio and a transport lifetime model, ionized impurities predominantly remote from the quantum well are identified as the dominant source of scattering events. The analysis of the well pronounced Shubnikov−de Haas oscillations reveals a high spin-orbit coupling with an effective g-factor of −38.4 in our samples. Along with the smooth surfaces and long mean free paths demonstrated, our InSb quantum wells are increasingly competitive for nanoscale implementations of Majorana mode devices.

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Section: Remaining Scattering Mechanismsmentioning

confidence: 99%

Limiting scattering processes in high-mobility InSb quantum wells grown on GaSb buffer systems

Lehner

Tschirky

Ihn

et al. 2018

Phys. Rev. Materials

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“…To determine the scattering mechanisms that led to the functional dependence of the mobility on density a series of elastic scattering calculations were performed. These calculations included scattering due to background impurities, remote impurities, charged dislocations, interface roughness and alloy scattering [20][21][22][23] . The calculations are outlined in Appendix A and follow the treatment of the transport relaxation time outlined by Stern and Howard 24 , where zero temperature is assumed, and inter-subband scattering, multiple scattering events, and correlations between ionized impurities are neglected.…”

Section: Manuscriptmentioning

confidence: 99%

Limits to mobility in InAs quantum wells with nearly lattice-matched barriers

et al. 2016

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The growth and the density dependence of the low temperature mobility of a series of twodimensional electron systems confined to un-intentionally doped, low extended defect density InAs quantum wells with Al 1-x Ga x Sb barriers are reported. The electron mobility limiting scattering mechanisms were determined by utilizing dual-gated devices to study the dependence of mobility on carrier density and electric field independently. Analysis of the possible scattering mechanisms indicate the mobility was limited primarily by rough interfaces in narrow quantum wells and a combination of alloy disorder and interface roughness in wide wells at high carrier density within the first occupied electronic sub-band. At low carrier density the functional dependence of the mobility on carrier density provided evidence of coulombic scattering from charged defects. A gate-tuned electron mobility exceeding 750,000 cm 2 /Vs was achieved at a at a sample temperature of 2 K. The possible scattering mechanisms leading to the observed density dependence of the mobility are discussed.Heterostructures were grown by molecular beam epitaxy (MBE) on GaSb:Te (001) substrates. Growth rate and composition calibrations were performed prior to the growth of the heterostructures and verified by reflection high energy electron diffraction patterns and oscillations during the growth of the heterostructures. In a previous work it was reported the carrier mobility and single-particle lifetime in InAs/(Al,Ga)Sb heterostructures are sensitive to the dislocation density in the epitaxial layers 18 .In this work the use of the nearly lattice matched substrate and buffer layers was intended to inhibit the formation of extended defects during MBE growth. Fig. 3(a) shows the 002 x-ray diffraction curve which was measured to obtain higher contrast between the multilayers that differed by the substitution on one of the zincblende structure sites. Fig. 3(b) shows the thin film x-ray diffraction reciprocal space map in the vicinity of the 002 and asymmetric 115 Bragg reflections of the GaSb substrate of sample D. In the 115 reciprocal space map, measured in a grazing incidence configuration, the substrate peak and the peak from the AlAs 1-y Sb y buffer layer are well resolved and indicate the buffer was nearly lattice matched but slightly tensile strained 5 to the substrate (y ~ 0.9). The threading dislocation densities of the films were measured by both etch pits using a solution of HF:H 2 O 2 :H 2 SO 4 :H 2 O similar to that reported by Aifer and Maximenko 19 and by electron channeling contrast imaging (ECCI) using a backscattering geometry in a field emission scanning electron microscope. ECCI analysis was performed using several diffraction vectors to mitigate unintentionally satisfying the invisibility criterion where the Burger's vector for a given dislocation is perpendicular to the diffraction vector. Fig. 3(b) shows an ECCI micrograph measured from the surface of the MBE grown film of sample D.Several lines of enhanced contrast are interpreted ...

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“…At this stage, we do not completely understand the precise correlation between the nucleation conditions and the 2DEG transport properties. Several mechanisms could be limiting the Hall-effect mobilities in the strained QW channels, such as rough heterointerfaces, Stark-effect scattering 12 , and hole-drag due to a co-existence of a two-dimensional hole gas (2DHG) channel at the bottom GaN/AlN interface 10 . A comprehensive study of transport is ongoing, and should help identify the lower measured electron mobilites in such heterostructures compared to 2DEGs on GaN substrates.…”

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confidence: 99%

Strained GaN quantum-well FETs on single crystal bulk AlN substrates

Ganguly

et al. 2017

Applied Physics Letters

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We report the first realization of molecular beam epitaxy grown strained GaN quantum well field-effect transistors on single-crystal bulk AlN substrates. The fabricated double heterostructure FETs exhibit a twodimensional electron gas (2DEG) density in excess of 2×10 13 /cm 2 . Ohmic contacts to the 2DEG channel were formed by n + GaN MBE regrowth process, with a contact resistance of 0.13 Ω·mm. Raman spectroscopy using the quantum well as an optical marker reveals the strain in the quantum well, and strain relaxation in the regrown GaN contacts. A 65-nm-long rectangular-gate device showed a record high DC drain current drive of 2.0 A/mm and peak extrinsic transconductance of 250 mS/mm. Small-signal RF performance of the device achieved current gain cutoff frequency f T ∼ 120 GHz. The DC and RF performance demonstrate that bulk AlN substrates offer an attractive alternative platform for strained quantum well nitride transistors for future high-voltage and high-power microwave applications.State-of-art gallium nitride based electronic devices have demonstrated excellent performance in highfrequency and high-power applications 1-5 . These devices are on thick GaN buffer layers, most of which are on SiC substrates for efficient thermal dissipation. The heteroepitaxially grown GaN layers inherently incorporate high density of dislocations (typically ∼ 10 9 /cm 2 ), which give rise to reliability issues and degrade breakdown characteristics.In this letter we show that thin strained GaN quantum well double heterostructures on bulk AlN substrates offer an attractive alternative approach for high-performance nitride electronics. To meet the scaling requirements for high-speed high-power RF applications, tight electrostatic control and quantum confinement of charge carriers are highly desired. The wide direct band gap of AlN (∼6.2 eV) and its large band offset with GaN offers the maximal vertical confinement of carriers in nitride channels. The large polarization charge of AlN induces high density two-dimensional electron gases (2DEG) in the quantum well, which is desired for high current drive and lateral scaling of gate lengths. The thermal conductivity of AlN, estimated 6 to be as high as ∼340 W/m·K can be comparable 7 to that of SiC ∼370 W/m·K, and offers the potential benefit of reducing thermal boundary resistance. Thus AlN simultaneously satisfies the conflicting requirements of high thermal conductivity and high electrical resistivity for high-power microwave electronics. Importantly, the low dislocation density (∼ 10 4 /cm 2 ) of single-crystal bulk AlN substrates has the potential for defect-free channels and barriers in principle, which is a promising prospective for improving thermal robustness, reliability, breakdown, and noise characteristics of these devices 8 . The presence of a very thin GaN quantum well active region embedded in the AlN/GaN/AlN double heta) Electronic mail: djena@cornell.edu. erostructure also enables selective optical-marker based Raman metrology of strain 9 present in the active layer...

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Stark-effect scattering in rough quantum wells

Cited by 17 publications

References 12 publications

Limiting scattering processes in high-mobility InSb quantum wells grown on GaSb buffer systems

Limiting scattering processes in high-mobility InSb quantum wells grown on GaSb buffer systems

Limits to mobility in InAs quantum wells with nearly lattice-matched barriers

Strained GaN quantum-well FETs on single crystal bulk AlN substrates

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