A quantitative analysis of electronic transport in n- and p-type modulation-doped GaAsBi/AlGaAs quantum well structures

Abstract

Electronic transport properties of as-grown and thermally annealed n-and p-type modulation-doped GaAsBi/AlGaAs quantum well (QW) structures were investigated. Hall mobility of as-grown, n-and p-type modulation doped QW structures are found from raw experimental data as ∼1414 and 95 cm 2 Vs −1 at room temperature. A comparison between reported two-dimensional (2D) electron density determined from the analyses of Shubnikov de Haas oscillations and the 2D Hall electron density indicates a presence of parallel conduction in barrier layer (AlGaAs) and QW layer (GaAsBi) in n-type samples, therefore a parallel channel conduction theory is used to separate the electron mobility in the QW and the barrier layers in n-type modulation doped GaAsBi/AlGaAs QW structure. The extracted electron mobility of the as-grown n-type GaAsBi/AlGaAs QW sample is determined as ∼5975 cm 2 Vs −1 at 4.2 K, which is closer to the electron mobility in GaAs. It is found that thermal annealing at lower temperature than growth temperature increases electron mobility of 2D electron gas, while annealing at higher temperature than growth temperature decreases electron mobility. The temperature dependence of the extracted electron mobility using parallel conduction approximation is analytically calculated by considering possible scattering mechanisms. Analysis of temperature-dependent electron mobility shows that the dominant scattering mechanisms are interface roughness (IFR), acoustic, and alloy-potential scatterings at low and intermediate temperature range, and IFR and optical phonon scattering at the high-temperature range in n-type modulation doped GaAsBi/AlGaAs QW structures.

High‐Field Electron‐Drift Velocity in n‐Type Modulation‐Doped GaAs0.96Bi0.04 Quantum Well Structure

“…Drift velocity of the electrons is determined usingwhere I is the current, and n (≈1.32 × 10 13 cm −2 ) is the carrier density in the sample as determined from Hall effect measurements. [ 15 ] w is the width of the channel. e is the fundamental electron charge.…”

“…The drift electron mobility is higher than the Hall mobility value as 1455 cm 2 Vs −1 found from Hall effect measurements on the same sample. [ 15 ] When the electric field is increased from ≈2.7 to ≈3.4 kV cm −1 (region II), the drift velocity saturates at ≈6.1 ×10 6 cm s −1 . Above 3.4 kV cm −1 electric field shown with the arrow in Figure 1a, the sample was burnt out and the current filament was generated due to the high carrier density in the sample.…”

“…The energy separation between the first quantized energy level in QW and barrier layer's conduction band edge as ≈0.159 eV is much lower than the difference between the first quantized energy level at the Γ valley and conduction band edge of the L satellite valley of GaAsBi QW layer as being ≈0.263 eV. [ 5,15–17 ] Thus, hot electrons in the central valley of the QW start transferring to the central valley of the barrier layer as a result of RST then as increasing electron temperature, and both RST and IVT contribute to the electronic transport of hot electrons. In order to clarify the amount of the transferred electrons, the transition rate between the layers should be calculated.…”

“…In these studies, the temperature dependence of carrier density and mobility and the effective mass for bulk GaAsBi have been determined. [10][11][12][13][14] In our previous papers, [15][16][17] we examined the temperature dependence of electron mobility, effective mass, and carrier density for the same sample studied here. We found that the charge transport mechanism takes place between the barrier layer and the quantum well (QW) channel in parallel conduction mode using Hall effect measurements and analysis of Shubnikov de Haas oscillations.…”

“…The drift electron mobility is higher than the Hall mobility value as 1455 cm 2 Vs À1 found from Hall effect measurements on the same sample. [15] When the electric field is increased from %2.7 to DOI: 10.1002/pssr.202200204…”