Magnetoresistance and hall effect of warm and nonequilibrium electrons in high-purity n-GaAs

The dependences of magnetoresistance and Hall coefficient on magnetic and electric fields are investigated in epitaxial n‐GaAs layers with shallow donor concentration Nd ⪅ 1014 cm−3. Measurements are carried out at 4.5 K in magnetic fields up to 3 T. The investigated samples have S‐shaped (current controlled) current‐voltage characteristics due to impact ionization of shallow impurities. The relative magnetoresistance scales as ΔQ ∝ exp Bα at weak electric fields, where α = 2.06 ± 0.04 and 0.54 ± 0.02 for weak and strong magnetic fields, respectively, and ΔQ ∝ Bβ close to the breakdown field Ebr, where β = 1.09 ± 0.02. In electric fields above breakdown (E > Ebr) the magnetoresistance is found to be proportional to Bγ with γ = 1.96 ± 0.08. The Hall coefficient decreases for E < Ebr and increases for E > Ebr with increasing magnetic field strength.