Quantum transport in high mobility modulation doped Ga0.25In0.75As/InP quantum wells

Abstract

We report on edge state transport in a ternary material, a modulation-doped InP/Ga0.25In0.75As/InP quantum well, where the electron transport takes place in the highly strained Ga0.25In0.75As layer. The electron mobility is, even though fundamentally limited by alloy-disorder scattering, determined by the two-dimensional electron concentration. By varying the distance between the modulation-doped layer and the two-dimensional electron gas we influence the single particle relaxation time but not the electron mobility. Special attention is paid to the effect of dislocation formation in the conducting Ga0.25In0.75As layer. In addition to the quantum Hall and the Shubnikov–de Haas effect a strong, nonlocal transport behavior, which is maintained after illumination, is observed. This effect is explained by the low defect density and the Fermi level pinning on the etched Ga0.25In0.75As surface, at an energy close to the same as the Fermi energy of the two-dimensional electron gas. Furthermore, overshoot effects of the quantum Hall plateaus introduced by the high and varying effective (many-body) g value are investigated. The g value is further addressed in an experiment on a wet etched quantum wire in which values enhanced up to around 45 were found.

Growth variations and scattering mechanisms in metamorphic In0.75Ga0.25As/In0.75 Al0.25As quantum wells grown by molecular beam epitaxy

“…A good fit can be made to each set of data by adjusting the background impurity level and the interface roughness. The extracted alloy disorder potential is 0.3 eV which agrees with the result, around 0.3 eV, reported by [7] for In 0.75 Ga 0.25 As however smaller than the value (0.5 eV) reported by [5]. The extracted background impurity level is of the order of 10 15 cm À 3 .…”

“…This decrease was also observed by Capotondi in their undoped relaxed structures [1] and Ramvall in their strained structures [7]; however, only two of the best mobility structures showed an increase in mobility after the minimum mobility. This feature, due to the second-subband population, is confirmed by multiple frequencies in the Shubnikov-de Haas oscillation as shown in Fig.…”

“…7. This had been observed by many researchers [24,17,7]. This could result from a number of reasons such as interface roughness, indium concentration modulation or anisotropic ordering appeared in the structures.…”

“…Scattering mechanisms in relaxed and strained InGaAs/InAlAs quantum wells have been studied by several researchers [1,2,7]. Their research has shown that scattering from background impurities limits the mobility at lower carrier densities, scattering from alloy disorder becomes more important at higher carrier densities.…”

Confinement properties of aGa0.25In0.75As∕InPquantum point contact

“…Our QPC is etched into a strained Ga 0.25 In 0.75 As/ InP heterostructure, 18,19 as shown schematically in the inset of Fig. 1.…”