Temperature-dependent charge-carrier transport between Si-δ-doped layers and AlGaAs/InGaAs/AlGaAs quantum well with various space layer thicknesses measured by Hall-effect analysis

Abstract

temperature (T = 40 ~ 300 K) dependence of Hall-effect analysis on the dual Si-δ-doped AlGaAs/ InGaAs/AlGaAs quantum-well (QW) structures with various space layer thicknesses (t S = 5, 10 and 15 nm) was performed. An interesting hysteresis behavior of electron sheet concentration [n 2D (T)] was observed for t S = 10 and 15 nm but not for t S = 5 nm. A model involving two different activation barriers encountered respectively by electrons in the active QW and by electrons in the δ-doped layers is proposed to account for the hysteresis behavior. However, for small enough t S (= 5 nm ≤ 2.5 s, where s = 2.0 nm is the standard deviation of the Gaussian fit to the Si-δ-doped profile), the distribution of Si dopants near active QW acted as a specific form of "modulation doping" and can not be regarded as an ideal δ-doping. These Si dopants nearby the active QW effectively increase the magnitude of n 2D , and hence no hysteresis curve was observed. Finally, effects from t S on the T-dependence of electron mobility in active QW channel are also discussed.

Disorder effect on intersubband optical absorption of n-type δ-doped quantum well in GaAs

“…If we compare the disordered density (ζ ̸ =0) and ordered one (ζ = 0), it is noted that the very weak disorder (ζ = 0.05) produces a slight reduction of the linear and the total absorption in both impurities concentration. Additionally, the weak disorder (ζ = 0.1) produces a reduction of α (1) rel and α Tot rel coefficients more than almost 20%. This means that the optical absorption properties are very sensitive to the variation of bidimensional density in DDQWs.…”

“…In the following of this work, it applies an external electric field F = 10 kV cm −1 on the δ-DDQWs (N 2d = 5 10 12 cm −2 and 7.5 10 12 cm −2 ), in order to analyze the influence of others kinds of structural disorder on the absorption properties. Especially, figure 2 shows the impact of the disordered electric field with different strength (ζ F = 0, 0.1, 0.3, 0.5) on the linear α (1) rel and total absorption coefficient α Tot rel in both the bidimensional densities. Figures 2(a) and (b) show that the absorption coefficients are insensible for all different disorder degrees of the applied electric field when the bidimensional density is N 2d = 7.5 ×10 12 cm −2 .…”

“…In fact, the large density (N 2d = 7.5×10 12 cm −2 ) strengths the potential confinement of δ-doped quantum well, provoking a reduction of the applied electric field influence on the first and on the fundamental state. Therefore, the fluctuations of F ζ are almost unable to modify the potential of the transition energy states (E i and E f ), which, produce α (1) rel and α Tot rel to remain practically unalterable. On the contrary, when the bidimensional density is low (N 2d = 5 ×10 12 cm −2 ), the strong fluctuations of the applied electric field (ζ F = 0.5) induce a perturbation of the electronic structure, consequently, cause a reduction in the absorption coefficients.…”

“…In equation ( 1), we assume all QWs are located along the z-axis. The linear (α (1) ) and nonlinear (α (3) ) optical absorption coefficient can be determined using Ahn's calculations [51], with the expressions:…”

“…Ref (ω)) an isolated well with carrier density N 2d = 5 × 10 12 cm −2 , in the transition from the ground state to the first excited state. α(1) …”