High sub-bandgap response and fast switching enabled by thermal quenching in carbon-doped semi-insulating GaN

TL;DR

This study demonstrates that carbon-doped GaN exhibits high sub-bandgap optical response and rapid switching due to thermal quenching effects, with potential applications in optical switching technologies.

Contribution

It provides new insights into the thermal quenching mechanism and switching kinetics of carbon-doped GaN under sub-bandgap illumination, highlighting its fast switching capabilities.

Findings

Achieved ON/OFF ratio exceeding 10^7 under low-irradiance 405-nm light.

Photocurrent decay is thermally quenched above ~300 K due to hole-emission-assisted recombination.

Thermal quenching accelerates photocurrent decay by up to five times, enabling faster switching.

Abstract

Carbon-doped GaN is a promising material for sub-bandgap triggered optical switches. When incorporated in GaN, carbon introduces deep compensating centers that enable defect-mediated extrinsic photoconductivity. Here, we investigate the optical responsivity and switching kinetics of semi-insulating carbon-doped GaN actuated by sub-bandgap blue illumination. A high ON/OFF ratio exceeding $\mathrm{10^7}$ is achieved under low-irradiance 405-nm excitation. Temperature-dependent transient measurements reveal that the photocurrent decay is thermally quenched above a crossover temperature of ~300 K. This behavior is attributed to hole-emission-assisted recombination. The extracted activation energies vary across samples; a commonly observed value of ~0.83 eV is attributed to the $\mathrm{C_N}$ defect. Notably, when heating above the crossover temperature, thermal quenching accelerates the photocurrent decay by up to a factor of five, enabling significantly faster switching.