Mobility Two-dimensional Electron Research Articles

Molecular beam epitaxial growth and structural design of In 0.52Al 0.48As/In 0.53Ga 0.47As/InP HEMTs

Lattice-matched In 0.52Al 0.48As and In 0.53Ga 0.47As layers and two-dimensional electron gas (2DEG) structures have been grown on (100) InP substrates by molecular beam epitaxy (MBE) with dimeric or tetrameric arsenic species. Surface morphology of 0.5 μm In 0.53Ga 0.47As layers is strongly influenced by the As 4 to group III flux ratio, and also by the arsenic species used in the growth. The RHEED oscillation study shows that the uses of As 2 or higher As 4 flux reduce the group III adatoms surface diffusion, hence improving the interface or surface roughness caused by the alloy clustering. This behavior is more obvious in the growth of In 0.53Ga 0.47As layers than In 0.52Al 0.48As. Two-dimensional electron mobilities of over 11,080 cm 2/V⋯s at 300 K and 33,500 cm 2/V⋯s at 77 K with sheet charge of 3.9×10 12 cm −2 have been achieved from this study.

Correlation length of interface roughness and its enhancement in molecular beam epitaxy grown GaAs/AlAs quantum wells studied by mobility measurement

We have studied the correlation length (Λ) of interface roughness in GaAs/AlAs quantum wells (QWs) prepared by molecular beam epitaxy (MBE). It is found that the mobility of two-dimensional electrons in very thin selectively doped GaAs/AlAs QW structures is substantially enhanced when the bottom AlAs barrier layer is prepared by alternate beam MBE and/or by the use of superlattice buffer layer below the QW. By measuring the electron concentration dependence of mobility and comparing with the theory of interface roughness scattering, we have found that Λ of the bottom (GaAs-on-AlAs) interface of the QW gets as large as 200–300 Å, when prepared by the modified growth technique, which is about three times as large as that (∼70 Å) by conventional MBE.

Theoretical limit of mobility of two-dimensional electrons in GaAs

The acoustic phonon limited mobility of two-dimensional electrons in an (001)AlGaAs/GaAs heterojunction is calculated. It exceeds the highest experimentally achieved value of mobility by approximately six times at the liquid helium temperature.

Maximum low-temperature mobility of two-dimensional electrons in heterojunctions with a thick spacer layer.

The calculation of the mobility of the two-dimensional electron gas limited by the remote ion scattering is presented which takes into account the correlation in the spatial distribution of the charged impurities caused by the Coulomb interaction. The correlation function of the charge is characterized by the freezing temperature ${\mathit{T}}_{0}$. The low-temperature distribution of the charge is supposed to be a snapshot of the equilibrium distribution corresponding to this temperature. At low enough ${\mathit{T}}_{0}$ this distribution corresponds to the ground state of the system consisting of the charged and neutral impurities. The effect of the correlation is shown to be very essential at low ${\mathit{T}}_{0}$ and at large spacer thickness. The numerical calculations are performed for modulation-doped ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs heterostructures. Input parameters are as follows: spacer width (s), temperature (${\mathit{T}}_{0}$), density of the channel electrons (${\mathit{N}}_{\mathit{s}}$), and density of the charge in the depletion layer (${\mathit{N}}_{\mathrm{depl}}$).

Electronic properties of two-dimensional electron gas in pseudomorphic In xGa 1− xAs/N-In 0.52Al 0.48As heterostructures

The two-dimensional (2D) electron concentration and mobility in pseudomorphic In x Ga 1- x As/N-In 0.52Al 0.48As ( x = 0.53, 0.64, and 0.75) heterostructures were studied. The electron concentration increased with the InAs mole fraction, x. This increase agreed with theoretical values when the variation in the conduction band discontinuity including biaxial compressive strain effect and in the 2D density of states was considered. Although the mobility increased with x at 300 K, the low temperature mobility (77 and 4.2 K) had a maximum at x = 0.64. Preliminary 1 μ m gate HEMTs using these heterostructures exhibited transconductances as high as 400 mS/mm for x = 0.53, 460 mS/mm for x = 0.64, and 560 mS/mm for x = 0.75.

Small‐Signal AC Mobility of Two‐Dimensional Hot Electrons in Semiconductor Quantum Wells at Low Temperatures

physica status solidi (b)Volume 148, Issue 1 p. K17-K22 Short Note Small-Signal AC Mobility of Two-Dimensional Hot Electrons in Semiconductor Quantum Wells at Low Temperatures D. Chattopadhyay, D. Chattopadhyay Institute of Radio Physics and Electronics, Calcutta Search for more papers by this authorP. C. Rakshit, P. C. Rakshit Institute of Radio Physics and Electronics, Calcutta Search for more papers by this authorC. K. Sarkar, C. K. Sarkar Institute of Radio Physics and Electronics, Calcutta Search for more papers by this author D. Chattopadhyay, D. Chattopadhyay Institute of Radio Physics and Electronics, Calcutta Search for more papers by this authorP. C. Rakshit, P. C. Rakshit Institute of Radio Physics and Electronics, Calcutta Search for more papers by this authorC. K. Sarkar, C. K. Sarkar Institute of Radio Physics and Electronics, Calcutta Search for more papers by this author First published: 1 July 1988 https://doi.org/10.1002/pssb.2221480145 92, Acharya Prafulla Chandra Road, Calcutta 700 009, India. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume148, Issue11 July 1988Pages K17-K22 RelatedInformation

Acoustic-phonon scattering in modulation-doped heterostructures.

We use recently determined values of conduction- and valence-band edge deformation potentials to analyze two-dimensional electron and hole mobilities in $\frac{\mathrm{GaAs}}{{\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}}\mathrm{As}$ modulation-doped heterostructures. Contrary to the commonly accepted view, it is shown that a consistent description of low-temperature mobility can be given only if the short-range deformation potential scattering is not screened by free carriers.

Interface roughness in AlAs/GaAs quantum wells characterized by the mobility of two-dimensional electrons

Interface roughness in AlAs/GaAs quantum wells characterized by the mobility of two-dimensional electrons

Interface roughness scattering in GaAs/AlAs quantum wells

We study experimentally and theoretically the influence of interface roughness on the mobility of two-dimensional electrons in modulation-doped AlAs/GaAs quantum wells. It is shown that interface roughness scattering is the dominant scattering mechanism in thin quantum wells with a well thickness Lw<60 Å, where electron mobilities are proportional to L6w, reaching 2×103 cm2/V s at Lw∼55 Å. From detailed comparison between theory and experiment, it is determined that the ‘‘GaAs-on-AlAs’’ interface grown by molecular beam epitaxy has a roughness with the height of 3–5 Å and a lateral size of 50–70 Å.

High mobility of two-dimensional electrons in Ga 1− xIn xAs/InP heterostructures grown by atmospheric pressure MOVPE

Atmospheric pressure MOVPE growth and characterization of successively InP, Ga 0.47In 0.53As and the 2DEG at the nominally undoped heterojunction are described. TEI, TMG, AsH 3 and PH 3 are the source reactants. The crystalline quality and the uniformity is indicated by double diffraction X-ray rocking curve with a FWHM (Ga x I 1− x As) as low as 24 arc s. The InP 4 K PL spectrum presents sharp exciton lines whereas in Ga x In 1− x As a single bound exciton related peak with a FWHM of 2.2 meV is detected. The best 77 K mobility for InP is 137,000 cm 2/V·s for a net carrier concentration of 1×10 14 cm −3. Ga x In 1− x As with a net doping level of about 2×10 15 cm −3 presents the best to date low temperature Hall mobilities: 11,400, 88,000 and 153,000 cm 2/V·s at 300, 77 and 10 K respectively. The two dimensional nature of the electrons in the undoped heterojunction is demonstrated and studied by Shubnikov-De Haas experiments. The first pronounced oscillations are detected for a magnetic field strength as low as 0.3 T, indicative of a very good quality material. Evidence for the occupation of two subbands is given, with an electron sheet concentration of n s1= 2.15 × 10 11 cm −2 and n s2 = 6.7×10 10 cm −2 respectively.

Electron-concentration dependence of the two-dimensional electron mobilities in modulation-doped AlGaAs/GaAs heterostructures

We have closely investigated the two-dimensional electron mobilities μ at low temperatures as a function of electron concentrations Ns in modulation-doped AlGaAs/GaAs heterojunctions, varying the thickness of undoped AlGaAs spacer and the shapes of the quantized electron wave functions. Measured mobilities are compared with theoretical calculations. The low-temperature mobilities in this system are well explained by the theory of scattering due to the remote ionized donors doped in the AlGaAs; this suggests the controllability of the ionized-impurity scattering process in this heterojunction system.

Electron-concentration dependence of the two-dimensional electron mobilities in modulation-doped AlGaAs/GaAs heterostructures

Electron-concentration dependence of the two-dimensional electron mobilities in modulation-doped AlGaAs/GaAs heterostructures

Mobility and diffusivity of two-dimensional degenerate hot electrons in polar semiconductor quantum wells

Mobility and diffusivity of degenerate hot electrons itinerant two-dimensionally in quantum wells are studied including the effect of electron-electron interactions. Occupancy of the first two subbands and lattice scattering via deformation potential acoustic and polar optic modes are considered. The degeneracy of the distribution function is found to affect the diffusivity more significantly than mobility. At large sheet carrier concentrations inter-subband scattering lowers the mobility as well as the diffusivity.

Calculated Electron Mobility of Two-Dimensional Electrons in AlInAs/InGaAs and InP/InGaAs Single Heterostructures

The self-consistent variational technique is used to calculate the mobility of two-dimensional electrons at the hetero-in-terfaces in AlInAs/InGaAs and InP/InGaAs single heterostructures. The sheet electron concentration dependence of the total mobility and each-scattering-limited mobility are shown. The predominance of the alloy-scattering-limited mobility is demonstrated. Model calculation of the two-dimensional electron mobility in an alloy-scattering-free InAs/GaAs monolayer superlattice with AlInAs as the barrier is also presented.

Mobility transition in the two-dimensional electron gas in GaAsAlGaAs heterostructures

Temperature dependence of the two-dimensional electron mobility (μ) in GaAsAlGaAs heterostructures, for 4.2K⪅ T⪅40K, shows a transition at μ∼1×10 5 cm 2 Vsec −1. This transition is demonstrated by a theoretical calculation to result from the interplay between screened impurity scattering and the acoustic phonon scattering. A systematic study of samples with μ>1×10 5 cm 2 Vsec −1 and a wide range of electron densities shows that a deformation potential E 1 = 13.5 eV, as suggested by Price, is needed to explain all the data.

Low temperature two-dimensional mobility of a GaAs heterolayer

The two-dimensional electron mobility for a GaAs single-interface heterolayer at low temperatures is computed, as a function of electron sheet density, in terms of the Fang-Howard-Stern model wave-function, for both deformation-coupled and piezoelectric-coupled scattering by acousticmode phonons. The temperature range of validity for this mobility proportional to 1/T is estimated. The unscreened mobilities are also given for comparison. The ion-scattering mobility, for various distances of the donor ion layer from the interface, is also computed, using the same model wave-function. It appears that, in the conditions of interest, lattice scattering will not dominate the overall mobility but can have a significant effect on it.

Low temperature two-dimensional mobility of a GaAs heterolayer

Abstract The two-dimensional electron mobility for a GaAs single-interface heterolayer at low temperatures is computed, as a function of electron sheet density, in terms of the Fang-Howard-Stern model wave-function, for both deformation-coupled and piezoelectric-coupled scattering by acousticmode phonons. The temperature range of validity for this mobility proportional to 1/T is estimated. The unscreened mobilities are also given for comparison. The ion-scattering mobility, for various distances of the donor ion layer from the interface, is also computed, using the same model wave-function. It appears that, in the conditions of interest, lattice scattering will not dominate the overall mobility but can have a significant effect on it.

High mobility of two-dimensional electrons at the GaAs/n-AlGaAs heterojunction interface

Mobility of the two-dimensional electron gas as high as 61 500 cm2/V sec, with a carrier concentration of 5.7×1011 cm−2, was obtained at 66 K in a selectively doped GaAs/n-AlGaAs heterojunction structure grown by molecular beam epitaxy. This mobility is a factor of 2–3 larger than any reported so far in similar structures.