Magnetotransport in InP-based dilute single δ layers

Abstract

We have investigated the magnetotransport in InP sulphur-doped 5-layer structures. In contrast to GaAs-based systems, it was possible to measure single 5 layers in the concentration range between 10" and 10' m where a metal-insulator transition is expected. At low magnetic fields perpendicular to the sample we observed a giant negative magnetoresistance ( -30%%uo at 4.2 K), followed by an exponential increase in magnetoresistance at high fields. The behavior of the minimum shows certain features of the quantum Hall efFect corresponding to a filling factor of 2. The experimental data are interpreted with the help of a strong-weak-localization transition-phase diagram in a disordered two-dimensional electron gas constructed using a simple lucid model.

Deep levels in GaAs due to Si δ doping

“…A possible explanation can be an inaccuracy of the theory based on an assumption of the homogeneous charge distribution in the plane of the ␦ layer. Our medium doped samples have concentrations only slightly above the value corresponding to the metal-insulator transition 12 (3 ϫ10 15 m Ϫ2 ) where the role of fluctuations of the donor concentration increases and the distribution of the fixed charge is far from the homogeneous one. Such an inhomogeneity leads to a local decrease of the concentration below the average value and hence to a further broadening of the electron wave function extent.…”

“…Moreover, because the ␦ doping produces a self-consistent potential well confining a two-dimensional ͑2D͒ electron system with a high degree of disorder, basic physical properties of the two-dimensional electron gas have been studied in ␦ layers mainly by magnetotransport and optical methods [8][9][10] with a special emphasis put on a detailed analysis of the influence of disorder on the transport and the localization in twodimensional systems. [11][12][13][14] An elementary characterization of the ␦ layers is often performed by a capacitance-voltage (C -V) measurement in structures where the ␦ layer is involved in a space charge region ͑SCR͒ of the Schottky barrier. A position of the layer and its sheet donor concentration can be determined from an apparent concentration profile calculated from the C -V curve.…”

Out-of-Plane Weak Localization in Two-Dimensional Electron Structures

“…It is a remarkable fact that this result has some common features with a quite recent [14,15] interpretation of the influence of the in-plane magnetic field on the electronic bilayer existing in wide quantum wells. To bring both these limiting cases together (i.e., insulating and conducting) the present Letter provides lacking experimental data on structures containing parallel 2D subsystems of electron concentrations from the range ͑10 15 10 16 m 22 ͒ where the metal-insulator transition in disordered 2D takes place [11]. The data obtained are interpreted using a model of potential fluctuations and the idea of the destruction of certain out-of-plane weakly localized orbits by parallel magnetic field.…”

“…Traditionally, the most striking, well established effect is the low temperature giant negative magnetoresistance observed in two-dimensional (2D) disordered structures with a variable range hopping regime in the perpendicular magnetic field [7][8][9]. On the contrary, sporadic analogous experiments with a magnetic field parallel to the 2D subsystem [10,11] gave evidence that this effect is not quite negligible in only the case where the structure contains two or more parallel 2D subsystems a tunneling distance apart. The theoretical treatment [12,13] has shown that the observed behavior of magnetoresistance is very likely due to the existence of weakly localized orbits incident with two adjacent 2D subsystems.…”

“…The donors randomly distributed over the plane of d layer, together with the acceptor background, introduce a strongly oscillating potential. The variation of the potential dc can be estimated as [11] dc e p…”