Two-Side Doping Effects on the Mobility of Carriers in Square Quantum Wells (original) (raw)
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Springer Proceedings in Physics
A variational approach is given for the effect from single-side modulation doping quantum well (QW). We obtained analytic expressions which describe the doping effects on the carrier distribution in the well, their roughness-induced scattering in the in-plane and screening by them. The calculation of the transport lifetimes is performed for holes in a SiGe/Ge/SiGe square QW, and the result is found in quantitative agreement with recently measured dependence on experimental conditions such as channel width and carrier density.
2007
The effects of optically exciting n-type and p-type one-side modulation-doped InGaAs/ GaAs quantum well structures were investigated by scanning the photoluminescence intensity profile on the sample's surface. An undoped quantum well was used as reference. Photoluminescence and carrier diffusion length measurements were carried out at increasing optical excitation densities. We found that the excitation density dependence of the carrier diffusion length in doped samples is quite different from that of the undoped sample. This difference is discussed in terms of the reduction of band bending/band-gap renormalization and carrier lifetime change due to the reduction of the two-dimensional carries gas density inside the quantum well upon intense laser illumination.
Physica B: Condensed Matter, 2018
We study the impact of non-square potential well structure on the electron mobility µ of double quantum well (DQW) based field effect transistors carved out of the Al x Ga 1-x As alloy. The barriers lying towards the substrate and surface sides of the DQW are delta doped with Si. We consider DQWs having V-shaped (VDQW), parabolic (PDQW), cubic (CDQW) and square (SDQW) potential wells to obtain the low temperature double subband electron mobility µ. We consider ionized impurity (Imp-) and alloy disorder (Al-) scatterings to calculate µ as a function of well width w and surface electron density N S. We show that the changes in the structure potentials influence the interplay of intersubband effects on the scattering mechanisms differently causing µ(VDQW) < µ(PDQW) ≅ µ(CDQW) as a function of w whereas µ(VDQW) < µ(PDQW) < µ(CDQW) as a function of Ns. We show that µ increases not only with increase in the width of the central barrier b but also decrease with the height of the non-square potentials. Our results can be utilized to analyze the effect of non-square quantum well potentials on the channel conductivity of the quantum well modulation doped field effect transistors.
Carrier transport in asymmetric multiple quantum well structures
2008
Carrier transport in semiconductor quantum wells relevant for high-speed properties of QW lasers and SOAs is addressed. The emphasis is on tunneling in asymmetric MQWs. It is shown that tunneling is occurring on the time scale of intraband scattering or shorter.
Semiconductor Science and Technology, 2014
Temperature and nitrogen dependence of 2D carrier mobility in as-grown and annealed Ga 1−x In x N y As 1−y /GaAs quantum well (QW) structures (x = 0.32; y = 0, 0.009, and 0.012) are investigated. An analytical model that accounts for the most prominent scattering mechanisms is used to explain the characteristic of temperature dependence of the carrier mobility. An expression for alloy scattering-limited mobility in N-related alloys is developed to explain the behavior of hole mobility for N-containing p-type samples. Analytical modeling of temperature dependence of the electron mobility indicates that N-related alloy scattering and interface roughness scattering are the dominant mechanism at the entire temperature range of interest. The temperature insensitivity of the electron mobility is explained in terms of the overriding effect of N-related alloy scattering and high 2D electron density. A deviation between theoretical and experimental electron mobility at low temperatures is observed not to have any dependency on N concentration. We, therefore, suggest that C NM interaction parameter of the band anti-crossing (BAC) model must be defined as temperature dependent in order to explain the observed low temperature characteristics of electron mobility. The hole mobility is mainly restricted by interface roughness and alloy scatterings at temperatures lower than 100 K, whilst high temperature hole mobility is drastically affected from optical phonon scattering. Moreover, the hole mobility at high temperatures exhibits an N-independent characteristic and hole density starts to increase at temperatures above 70 K, which is explained using the concept of parallel conduction. Extraction of the hole density in each transport channel (QW and barrier) by using a simple parallel conduction extraction method (SPCEM) shows that, in p-type samples, low temperature hole mobility takes place in quantum well, while as temperature increases barrier channel also contribute to the hole mobility and becomes dominant at high temperatures. The experimental and calculated Hall mobility results reveal that thermal annealing has decreased interface roughness and alloy scatterings.
2005
In this paper, the low-field carrier mobility is investigated for quasi-2D electrons in a n-doped In 0.53 Ga 0.47 As/InP single symmetric quantum well. An accurate variational scheme is developed in view to determine the subband structure in this lattice-matched heterostructure. In this scheme, the Schrödinger-Poisson coupled equations are solved observing adequate matching conditions at the heterointerfaces, as well as exchange-correlation corrections to the Hartree potential. The results allowed us to compute the main scattering rates. Some interchanges in these scattering rates were found with respect to the limitation of electron mobility by varying the well and the spacer widths.
Philosophical Magazine, 2019
We study the effect of the external electric field F ext on the low-temperature electron mobility μ in an asymmetrically doped Al x Ga 1-x As based V-shaped double quantum well (VDQW) structure. We show that nonlinearity of µ occurs under double subband occupancy on account of intersubband effects. The field F ext alters the VDQW potential leading to transfer of subband wave functions between the wells, which affects the scattering potentials and hence μ. In the VDQW structure, due to the alloy channel layer, the alloy disorder (Al-) scattering happens to be significant along with the ionised impurity (Imp-) scattering. The non-linear behaviour of μ is because of μ Imp , while the overall magnitude of μ is mostly due to μ Al. The increase of difference in the doping concentrations of the outer barriers increases the nonlinearity of μ. The oscillatory character of μ is amended by varying the width of the well and barrier and also the height of the VDQW. Our results can be used to study VDQW based nanoscale field effect transistor structures.
Two-subband electron transport in nonideal quantum wells
Physical Review B, 2000
Electron transport in nonideal quantum wells (QW) with large-scale variations of energy levels is studied when two subbands are occupied. Although the mean fluctuations of these two levels are screened by the in-plane redistribution of electrons, the energies of both levels remain nonuniform over the plane. The effect of random inhomogeneities on the classical transport is studied within the framework of a local response approach for weak disorder. Both short-range and small-angle scattering mechanisms are considered. Magnetotransport characteristics and the modulation of the effective conductivity by transverse voltage are evaluated for different kinds of confinement potentials (hard wall QW, parabolic QW, and stepped QW).
Electron mobility in the GaAs/InGaAs/GaAs quantum wells
Semiconductor Physics Quantum Electronics and Optoelectronics, 2013
The temperature dependence of the electron lateral mobility in quantum wells of the GaAs/InGaAs/GaAs heterostructures with delta-like doping has been studied. Two types of sample doping -in the quantum well and in the adjacent barrier at a small distance from the well -were used. In the case of shallow wells, in such structures the experimental results may be well described by known electron scattering mechanisms taking into account the shape of real envelope wave functions and band bending due to non-uniform distribution of the positive and negative space charges along the growth direction of heterostructure layers. In the case of delta-like doping in the well, a good agreement between experiment and calculations is achieved, if one takes into account a contribution to electron transport of the states of the impurity band formed by the deltaimpurity beneath the bottom of the lowest quantum subband.