In this work, homojunction interfacial workfunction internal photoemission (HIWIP) detectors based on GaAs, and heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors based mainly on GaAs/Al_xGa_1-xAs material system are presented. Design principles of HIWIP and HEIWIP detectors, such as free carrier absorption, photocarrier generation, photoemission, and responsivity, are discussed. Homojunction detectors based on p-type GaAs were found to limit their operating wavelength range. This is mainly due to band depletion arising through carrier transitions from heavy/light hole bands to split off band.

Enhancement of detector response using resonance cavity architecture is demonstrated. Threshold wavelength extension of HEIWIPs by varying the Al composition of their barrier was investigated. The threshold limit of ~ 3.3 THz (92 µm) due to a practical Al fraction limit of ~0.005 can be overcome by replacing GaAs emitters in GaAs/Al_xGa_1-xAs HEIWIPs with Al_xGa_1-xAs emitters. Based on the terahertz absorption results in epilayers, an Al_xGa_1-xAs/GaAs HEIWIP detector was designed and the extension of threshold frequency (f₀) to 2.3 THz was successfully demonstrated.

In a different study, switching in GaAs/Al_xGa_1-xAs heterostructures from a tunneling dominated low conductance branch to thermal emission dominated high conductance branch was investigated. This bistability leads to neuron-like voltage pulses observed in some heterostructure devices. The bias voltage needed for switching was found to decrease with the increasing device temperature.