Electrical Transport in a Semimetal–Semiconductor Nanocomposite

Measurements are presented on the low-field electrical conductivity and moderate-field current–voltage characteristics in a nanocomposite structure of ErAs particles in an $\hbox{In}_{0.53}\hbox{Ga}_{0.47}\hbox{As}$ host with Be compensation. The electrical conductivity displays strong temperature dependence with two types of transport mechanisms. At ${\sim}\hbox{205}$ K and above, the low-field conductivity appears to be dominated by free electrons in $\hbox{In}_{0.53}\hbox{Ga}_{0.47}\hbox{As}$. Between 55 and 205 K, the conductivity is well explained by variable-range hopping, $\sigma = A \exp(-B/T^{1/4}$), via Mott's law. The transport displays a soft breakdown effect at moderate bias fields that grows in threshold field with decreasing temperature. This is attributed to impact ionization of the Be dopants.