Power loss mechanisms in n-type modulation-doped AlGaAs/GaAsBi quantum well heterostructures

Abstract

We report on the power loss mechanisms of hot electrons in as-grown and annealed n-type modulation-doped Al 0.15 Ga 0.85 As/GaAs 1-x Bi x (x = 0 and 0.04) quantum well structures considering acoustic phonon interactions via the deformation potential (non-polar) and piezoelectric (polar) scatterings. The two-dimensional (2D) electron gas is heated by applying various electric fields under a steady-state magnetic field, and the effect of the applied electric field on the Shubnikov de Haas (SdH) oscillations is analyzed to investigate the power loss mechanism. The temperature of hot electrons (T e ) has been obtained by comparing the lattice temperature and applied electric field dependencies of the SdH oscillation amplitude. The hot electron temperature is almost the same for both Bi-free and Bi-containing samples except for the sample annealed at a higher temperature (700 • C) than the growth temperature of GaAsBi. The electron temperature dependence of power loss is analyzed using current theoretical analytic models derived for 2D semiconductors. We find that energy relaxation occurs in the intermediate temperature regime, including mixing of piezoelectric and deformation potential scattering. The power loss of hot electrons is found to be proportional to (T γ e − T γ L ) with γ in the range from 2.4 to 4.2, which indicates that the hot electron relaxation is due to acoustic phonon scatterings via unscreened deformation potential and piezoelectric scattering. It is found that deformation potential scattering is dominant over piezoelectric scattering in the Bi-free sample, while the incorporation of Bi into the GaAs lattice makes these processes comparable. After thermal annealing at lower than growth temperature (350 • C), the scattering mechanism switches from deformation potential to piezoelectric scattering. After thermal annealing at higher than growth temperature (700 • C), the theoretical model does not fit to the experimental results due to degradation of the sample.

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

“…The QW GaAsBi layer contained %4% Bi. [5,[15][16][17] The sample was fabricated in Hall bar geometry using conventional photolithographic methods for high-electric field measurements. In the measurement, Hall arm with of 750 μm (length) Â 100 μm (width) was used.…”

“…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 parameters are taken from our previous studies. [15][16][17] In our previous studies, we extract the electron mobility in the barrier layer and QW layer from Hall effect results due to the parallel conduction and we utilize here to calculate the hot electron temperature in the barrier and the QW layer. The electron temperature in the QW layer is much greater than that in the barrier layer because the electron mobility is larger in GaAs 0.96 Bi 0.04 QW layer (4780 cm 2 Vs À1 ) than in barrier layer (631 cm 2 Vs À1 ).…”

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

“…Ludewig et al showed that this AlGaAs layer for the barrier is good at carrier confinement within quantum well (QW) layers [12]. Contrary to bulk and epilayer GaAsBi materials, there are limited studies on the investigation of the electrical transport mechanism of the low dimensional GaAsBi structures apart from our previously published papers [13,14]. In our previous studies on n-type modulation doped GaAsBi/ AlGaAs QW structures, we determined fundamental electrical transport parameters such as electron effective mass, quantum mobility, the carrier density in QW, Fermi level position, and deformation potential energy at low temperatures.…”