Electron Mobility in Al_xGa_1−xAs Based Square‐Parabolic Double Quantum Well HEMT Structure − Effect of Asymmetric Doping Profile

Abstract

We study the asymmetric doping dependence of electron mobility µ in an AlxGa1−xAs based square‐parabolic double quantum well (SPDQW) high electron mobility transistor (HEMT) structure. We consider the square (parabolic) well and doping concentration Nd1 (Nd2) in the barrier toward the substrate (surface) of the structure. Keeping Nd1 fixed, variation of Nd2 leads to the resonance of subband states of the individual wells at a Nd2 > Nd1. The mobility is calculated as a function of Nd2 by considering ionized impuritiy (ii‐), interface roughness (ir‐) and alloy disorder (al‐) scatterings. We show that near resonance of the subband states, the dip in µ arises due to the substantial change in the ir‐ and al‐intersubband scattering rate matrix elements. The dip in μ is significant in SPDQW because of the sharp variations of subband wave functions between the wells due to the asymmetric potential profiles. Enhancement of the well width and central barrier width increases μ and sharpness of the dip in μ. Keeping Nd2 constant and Nd1 varying, the resonance occurs at Nd1 < Nd2 with similar nonlinearities in μ. Our results of µ can be utilized for the analysis of the performance of the HEMT devices.

Effect of Strain on Electron Transport and Quantum Lifetimes in InxGa1−xAs/In0.52Al0.48As Modulation Doped Double Quantum Well‐Based High Electron Mobility Transistor Structures

“…It is assumed that all the dopants are ionized and the electrons diffuse into the adjacent wells. Hence, the impurity n I (z) and electron concentrations n (z) perpendicular to the interface plane (say z) are written as follows: [29][30][31]…”

“…[29] We show V(z), Ψ 0 , Ψ 1 , E 0 , E 1 , and E F of the hybrid strained structure for w = 100 Å, b = 30 Å, s = 50 Å, d = 20 Å, and N d = 1 Â 10 18 cm À3 in Figure 1b. At low temperatures, the surface electron density n s can be expressed as: [29][30][31]…”

“…In this work, the ionized impurity (V ii nl ðqÞ), interface roughness (V ir nl ðqÞ), and alloy disorder (V al nl ðqÞ) screened scattering potentials are considered to calculate the corresponding α nl and β nl as expressed in Equation ( 13) and ( 14), respectively. The following screened scattering potentials can be expressed as: [30,31]…”

Studies on the nonlinear optical properties of two-step GaAs/Ga1−x Al x As quantum well

“…It is worth mentioning that one of the building blocks for semiconductor devices design are, undoubtedly, high quality heterostructures as discussed above, and among the wide quantity of possibilities, the coupled double QW structures, with different shapes and doping profile, are of paramount importance [7][8][9][10][11], because they can be used to tune linear and nonlinear optical properties that can be the intersubband absorption coefficient (AC) [12], the relative refractive index change (RIC) [11], second (third) order harmonic generation and nonlinear optical rectification [9], phase-dependent intersubband optical properties of asymmetric coupled QWs -just to give some examples-as a function of the electric and magnetic field, hydrostatic pressure, barrier doping profiles etc, the coupled double QW can also be used for field effect transistor applications [8,13]. Even, multiple QWs semiconductor nano-structures are of interest for optical properties, as the intersubband AC, that can be tuned by an applied electric field [14].…”

Electron transport in Al x Ga1−x As based double quantum well modulation doped field effect transistor structure: effect of non-square potential profile

“…The specific nature of these potentials also causes dramatic change in the electrical and optical properties of the system [4,7,9]. The potentials like parabolic [1][2][3][4], triangular [5][6][7][8][9], graded [10][11][12], V-shaped [13][14][15], cubic [14,15], inverse-parabolic [16][17][18], semi-parabolic [19,20], inverse V-shaped [21], semi V-shaped [22], square-parabolic [23], Gaussian [24] etc are the examples of such systems. Light emitting diodes based on triangular-shaped QWs have more internal quantum efficiency compared to that of rectangular ones [6].…”