1550 nm compatible ultrafast photoconductive material based on a GaAs/ErAs/GaAs heterostructure

TL;DR

This paper reports on a GaAs/ErAs/GaAs heterostructure exhibiting sub-bandgap absorption and ultrafast carrier relaxation at 1550 nm, making it suitable for high-speed terahertz devices in telecommunications.

Contribution

It introduces a novel heterostructure with ultrafast photo-response at 1550 nm, demonstrating potential for high-speed THz applications.

Findings

Carrier lifetime as low as 190 fs at 1550 nm

Two distinct absorption peaks from interfacial states and sub-bandgap transitions

Potential for high-critical-breakdown-field THz devices

Abstract

The sub-bandgap absorption and ultrafast relaxation in a GaAs/ErAs/GaAs heterostructure are reported. The infrared absorption and 1550 nm-excited ultrafast photo-response are studied by Fourier transform infrared (FTIR) spectrometry and time-domain pump-probe technique. The two absorption peaks located at 2.0 um (0.62 eV) and 2.7 um (0.45 eV) are originated from the ErAs/GaAs interfacial Schottky states and sub-bandgap transition within GaAs, respectively. The photo-induced carrier lifetime, excited using 1550 nm light, is measured to be as low as 190 fs for the GaAs/ErAs/GaAs heterostructure, making it a promising material for 1550-nm-technology-compatible, high critical-breakdown-field THz devices. The relaxation mechanism is proposed and the functionality of ErAs is revealed.