pnpn and npn Heterostructural Optoelectronic Devices

Abstract

An ohmic-contact pnpn triangular-barrier optoelectronic switch (TBOS) has been fabricated. The triangular barrier is formed by inserting an InGaAs p-type delta-doped (δ(p+)) quantum well between two n--GaAs layers. Due to the hole accumulation in the δ(p+) well and the avalanche multiplication in the reverse-biased region, an S-shaped negative differential resistance (NDR) is obtained in the device characteristics. With a replacement of the ohmic-contact p-type cap layer with a Schottky-contact n-type layer in the pnpn TBOS, a Schottky-contact npn TBOS has also been proposed. A double S-shaped NDR phenomenon is observed in the npn TBOS characteristics due to the hole accumulation in the δ(p+) well and the sequential avalanche multiplications in the reverse-biased region and Schottky-contact junction. Both devices show a flexible optical function as a result of the triangular barrier heights associated with incident light.