Electron Energy Relaxation via Acoustic Phonon Emission in GaAs/Ga1?xAlxAs Multiple Quantum Wells: Effects of Base Lattice Temperature

Abstract

The two-dimensional (2D) electron energy relaxation associated with acoustic phonon emission in GaAs/Ga 1--x Al x As multiple quantum wells (MQW) has been investigated using hot-electron Shubnikov-de Haas (SdH) effect measurements performed at three different base lattice temperatures T L0 ffi 1.7, 3.5 and 5.9 K. The modulation-doped MQW samples studied have quantum well widths L Z = 51, 75 and 78 A, and only the lowest subband in each sample is populated with a 2D electron density of about 1.10 Â 10 16 m --2 . The electron temperature (T e ) has been determined from the lattice-temperature and electric-field dependencies of the amplitude of the SdH oscillations. The energy-loss rates show a power-law dependence on T e with an exponent g, which depends on T L0 . The experimental results are compared with the current theoretical models for power loss in 2D and 3D semiconductors, which include both piezoelectric and deformation-potential scattering. The electron-temperature dependence of power loss, determined experimentally at liquid-helium temperatures with T L0 ffi 1.7 K, fits well to both the 2D and 3D theoretical models in the low-temperature regime, while the results at T L0 ffi 3.5 and 5.9 K fit best to those in the intermediate-temperature regime. The results provide useful information about the relative magnitude of the deformation-potential and piezoelectric contributions to power loss.

Energy Relaxation Rates in AlInN/AlN/GaN Heterostructures

“…This indicates that the experiments were carried out in the low-temperature regime and that the energy relaxation is due to acoustic phonon emission via mixed unscreened piezoelectric and deformation potential interactions. 2,49 We, therefore, fitted the experimental P(T e ) data, obtained from the measurements at T L0 % 1.8 K, to the analytical expressions for power loss in the lowtemperature regime (Fig. 8).…”

“…This is probably because the ideal quantum-well approximation in the extreme quantum limit, which was used in the 2D power loss calculations, predicts an enhancement in the confined electron-acoustic phonon interaction, compared with the case in a real triangle quantum well with finite barriers in our Al 0.83 In 0.17 N/AlN/GaN heterostructure. 2,3,7,49 Furthermore, the existing 2D theories use the bulk phonon approximation, which requires consideration of the confinement and folding of the longitudinal and transverse acoustic modes.…”

Energy relaxation studies in In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As two-dimensional electron gases and quantum wires

“…In LT2D, however, multiple regimes are present and these data are fitted with the function 2.3P (T 3 ) + 0.6P (T 5 ) to yield a better picture where screened and unscreened couplings exist with different magnitudes. The exponent 3 is seen in experiments [7,11,12] where it is attributed to a dominant unscreened piezoelectric coupling. Magnetic confinement of the electron-phonon interaction volume was suggested [13] as a possible cause for the exponent of 3, but no magnetic field dependence in seen in our data to confirm this.…”

Energy relaxations of hot electrons in AlGaN/AlN/GaN heterostructures grown by MOCVD on sapphire and 6H-SiC substrates

“…Therefore, electron energy loss mechanisms and rates can be determined from the electron temperature dependence of the power loss using the power balance equations [37]:…”