Linear magnetoresistance due to multiple-electron scattering by low-mobility islands in an inhomogeneous conductor

Abstract

Linear transverse magnetoresistance is commonly observed in many material systems including semimetals, narrow band-gap semiconductors, multi-layer graphene and topological insulators. It can originate in an inhomogeneous conductor from distortions in the current paths induced by macroscopic spatial fluctuations in the carrier mobility and it has been explained using a phenomenological semiclassical random resistor network model. However, the link between the linear magnetoresistance and the microscopic nature of the electron dynamics remains unknown. Here we demonstrate how the linear magnetoresistance arises from the stochastic behaviour of the electronic cycloidal trajectories around low-mobility islands in high-mobility inhomogeneous conductors and that this process is only weakly affected by the applied electric field strength. Also, we establish a quantitative link between the island morphology and the strength of linear magnetoresistance of relevance for future applications.

Impact ionization and large room-temperature magnetoresistance in micron-sized high-mobility InAs channels

“…This model describes well our observation of linear MR at low applied electric fields and high B z with r i = 1.5 × 10 12 s −1 , r e = 2.5 × 10 14 s −1 , = 0.5 μm and f = 0.05 (Table I; Ref. [19]). …”

“…Figure 7 shows the room temperature I-V characteristics for three devices with L = 2.6, 2.4, and 5.8 μm and W = 10, 5, and 10 μm at B z = 0 and 1 T (T = 300 K) corresponding to an aspect ratio L/W of 0.26, 0.48 and 0.58. In all structures we have measured a large room-temperature MR, exceeding 100% at B z = 1 T and V ß 1 V; also, we note that the presence of nonhomogeneities in the layers affects the strength of the MR [19], thus making it difficult to identify a systematic dependence on the aspect ratio L/W .…”

“…Since our InAs epilayers are grown on highly lattice-mismatched GaAs, threading dislocations tend to form at the epilayer/substrate interface and introduce macroscopic (>0.1 μm) inhomogeneities, leading to strong linear MR, as reported in Ref. [19]. In this previous paper, inhomogeneity was introduced in the Monte Carlo simulations by placing low-mobility islands randomly within the xy plane.…”

“…An earlier paper demonstrated that Hall bars and twoterminal devices based on InAs exhibit a linear MR over an extended range of applied magnetic fields B up to 50 T [19]. Here we focus on the effects of impact ionization on the MR at low applied magnetic fields up to 1 T. The magnetic field B was generated either by a superconducting magnet or a room-temperature electromagnet and was applied parallel or perpendicular to the growth axis z; i.e., B = [0, 0, B z ] or B = [B x , 0, 0].…”

Granularity Controlled Nonsaturating Linear Magnetoresistance in Topological Insulator Bi2Te3 Films

“…Based on these two key features of experimental systems, many theoretical efforts have also put forward to explain the LMR. [8][9][10][11][12][13][14][15] Among the theoretical models, the so-called 'quantum MR' theory by Abrikosov is based on the readiness of zero-gap semiconductor being in the high field quantum limit where only one Landau level is occupied and a non-saturating MR is possible. 8,9 Emphasizing the importance of sample inhomogeneity and distorted current distribution, a phenomenological semiclassical random resistor network model by Parish and Littlewood was able to explain the linear MR using classical physics.…”