Observation of multi-state negative differential conductivity in periodic delta-doped superlattice

A novel multi-state S-shaped negative differential conductivity (NDC) δ-doped superlattice structure with long period (Z_p =600 Å) is observed and investigated. The multi-state NDC originates from a sequential sub-avalanche multiplication in the superlattice periods. Three different GaAs superlattices, i.e. one-period, three-period, and nine-period δ(n⁺)-i-δ(p⁺ )-i δ-doped superlattices, were used. A different number of S-shaped NDCs are exhibited in each superlattice. An interesting hysteresis phenomenon was also apparent in the nine-period superlattice structure. It was attributed to the existence of heavy `trapped´ holes