The Hybrid Triangular Barrier (HTB) Photodiode consists of a staircase structure of AlGaAs and GaAs. When a bias is applied to this device bound states are formed inside of the barrier. Tunneling through these states gives rise to a Negative Differential Resistance (NDR) region in the current-voltage curve. This work investigates the possibility of using the NDR region to detect infrared (interband transitions) and Terahertz (intraband transitions) radiation.
The structure's transmission coefficient was modeled utilizing the Transfer Matrix Method (TMM) and the current-voltage characterizations were modeled using the commercial software NanoElectronic Modeling (NEMO) package. The devices were grown by Molecular Beam Epitaxy (MBE) and processed using standard photolithography techniques. Characterization of the devices consisted of current-voltage and photoresponse measurements. For the first time NDR was experimentally observed in this structure. A good agreement was found to exist between the theoretical and experimental current-voltage curves. Although no decisive photoresponse measurements were made, a theoretical model of the photoresponse of the device was developed. The theoretical response indicates that the device may work as a Terahertz detector.
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