The effect of high magnetic field on the photoresponse of Si:B structures with blocked conductivity in the impurity band

Abstract

The dependence of photoconductivity on the magnetic field has been studied for Si:B blocked-impurity-band (BIB) structures with the boron impurity concentration of ∼1018 cm−3 in the active layer. Measurements were performed in the magnetic field B up to 30 T with the pulse length of 0.8 s in the temperature range T = 4.2−9 K, under irradiation of structures with the room-temperature background with ∼1016 photons/(cm2 s) intensity. It is established that, in the longitudinal configuration and with the magnetic field parallel to the electric field, the photocurrent decreases as B increases, mainly due to a decrease in the hole multiplication factor M in the magnetic field and/or an increase in the activation energy for hopping conductivity in the active layer. At T = 4.2 K, the photocurrent can drop by a factor of several tens. At the same time, at low bias voltage V b , when M ≈ 1, and at higher temperatures, T ≈ 9 K, the photocurrent decreases no more than twofold in the field of ∼30 T. It is found also that in the transverse configuration (with the magnetic field perpendicular to the electric field), the effect of the magnetic field on the photoresponse of a structure significantly increases (more than by an order of magnitude at T = 4.2 K). This fact can be explained by the accumulation of carriers in the blocking (undoped) layer of a BIB structure, which is related to increasing time of the hole flight across this layer due to high mobility of holes and strong bending of their trajectories in the transverse configuration.