Irreversible increase of the low-temperature paramagnetism in GaAs substrates

The magnetic susceptibility of undoped GaAs substrates is measured from 2 to 300 K. It comprises two types of temperature-dependent net-paramagnetic contributions. One is a Van Vleck-type paramagnetic contribution which scales inversely with the band gap of the semiconductor and thus increases up to room temperature. The other resembles a Langevin-type paramagnetism which sets in only at low temperatures after certain thermal cycling procedures. © 2006 American Institute of Physics.