DFG Research Grant: Tunable Quantum Photoconductor for Efficiency-Enhanced THz Switches (QPC-Switch)


The goal of the proposed project is to investigate a novel approach for the realisation of ultrafast switching in semiconductor quantum-well photoconductive structures and to achieve ultrafast optical switching times of <1ps. The results of the investigation are to be applied to THz emitters and detectors. The photoconductive structure, referred to as a Quantum Photoconductor (QPC), is designed to absorb an ultra-short light pulse with wavelength near 1.55 micrometer that has a voltage bias across it, conduct current during the photocarrier lifetime, and become nearly insulating again after a very short time due to rapid carrier recombination. The resulting current spike can be used to generate high-frequency electromagnetic radiation, in this case in the THz part of the spectrum. A central part of the goal lies in realizing structures that simultaneously allow very high carrier mobility andshort carrier lifetimes. These seemingly contradictory requirements can be achieved by designing the structure to separate regions, one doped with deep levels to promote recombination and another that is undoped for high mobility. These regions should be engineered so that electrons in the ground state subband overlap with the deep-level region and electrons in an excited state subband do not, but are located in the high-mobility regions. The proposal describes three objectives: the investigation of Fe as a deep level within a InGaAs/InAlAs heterostructure, the investigation of Ru and Rh as more exotic deep levels, and the optimisation of the entire structure for THz detectors and emitters.
The goal of the proposed project is to investigate a novel approach for the realisation of ultrafast switching in semiconductor quantum-well photoconductive structures and to achieve ultrafast optical switching times of <1ps. The results of the investigation are to be applied to THz emitters and detectors. The photoconductive structure, referred to as a Quantum Photoconductor (QPC), is designed to absorb an ultra-short light pulse with wavelength near 1.55 micrometer that has a voltage bias across it, conduct current during the photocarrier lifetime, and become nearly insulating again after a very short time due to rapid carrier recombination. The resulting current spike can be used to generate high-frequency electromagnetic radiation, in this case in the THz part of the spectrum. A central part of the goal lies in realizing structures that simultaneously allow very high carrier mobility andshort carrier lifetimes. These seemingly contradictory requirements can be achieved by designing the structure to separate regions, one doped with deep levels to promote recombination and another that is undoped for high mobility. These regions should be engineered so that electrons in the ground state subband overlap with the deep-level region and electrons in an excited state subband do not, but are located in the high-mobility regions. The proposal describes three objectives: the investigation of Fe as a deep level within a InGaAs/InAlAs heterostructure, the investigation of Ru and Rh as more exotic deep levels, and the optimisation of the entire structure for THz detectors and emitters.


Principal Investigators
Masselink, W. Ted Ph. D. Prof. (Details) (Experimental Physics / Elementary Stimulation and Transport in Solids)

Duration of Project
Start date: 06/2016
End date: 03/2019

Research Areas
Communications, High-Frequency and Network Technology, Theoretical Electrical Engineering

Last updated on 2021-23-12 at 11:12