Magnetoresistance of n-GaAs at filamentary current flow

Abstract

Abstract. A large number of sharp structures are observed in the 4.2 K magnetoresistance of n-GaAs biased above impurity breakdown in a regime where current flow is filamentary. Most of the structures cannot be attributed to spectral properties of the semiconductor such as impact excitation of shallow donors or the magnetoimpurity effect. Experimental results give evidence that these structures are caused by a redistribution of the filamentary current flow when one filament border is swept across an imperfection in the material.

Discontinuities and Hysteresis in the I–V Characteristics of n-GaAs at Low Temperatures

“…1a) are shifted to higher currents at the present orientation of the magnetic field, because the Lorentz force acts to the left and the scratches are at the right. Similar structures in the current±voltage characteristics depending on the orientation of an external magnetic field have been previously observed by Proshin et al [10].…”

“…External magnetic fields may substantially change current voltage characteristics [7,10]. Besides destabilizing filamentary current flow [7] magnetic field induced discontinuities and hystereses have been observed.…”

“…Previous investigations of far-infrared photoconductivity [9] and magnetoresistance [10] of n-GaAs have shown that most of such features are different for different orientation of the current or the magnetic field and depend on the contacts. These structures in the I ±V characteristic were tentatively attributed to imperfections in the sample material, which represent an obstacle to the spreading of the filament.…”

Electron mobility measurement inn−GaAsat low-temperature impurity breakdown

“…An analogous filament-pinning effect may be observed also due to material imperfections. 19,20 The arrangement of filaments in Figs. 1͑a͒ and 1͑b͒ are obtained for the same current.…”

“…The vertical part of the characteristic reflects abrupt changes in the filament arrangement, as well as the continuous growth of filament widths. 19,20 The sample conductivity becomes almost constant as the whole width of the sample becomes filled with the high-conducting phase. Upon applying a perpendicular magnetic field the filaments are bent and tilted due to the Lorentz force, 15 as seen in Fig.…”