The potential of wide band-gap semiconductor materials in laser-induced semiconductor switches

Laser induced Semiconductor Switches (LSS), comprised of a gap antenna deposited on a semiconductor substrate and photoexcited by a pulsed laser, are the primary source of THz radiation utilized in time-domain spectroscopy (TDS). THz-TDS applications such as standoff detection and imaging would greatly benefit from greater amounts of power coupled into free space radiation from these sources. The most common LSS device is based on low temperature-grown (LT) GaAs photoexcited by Ti:sapphire lasers, but its power performance is fundamentally limited by low breakdown voltage. By contrast, wide band-gap semiconductor-based LSS devices have much higher breakdown voltage and could provide higher radiant power efficiency but must be photoexcited blue or ultraviolet pulsed lasers. Here we report an experimental and theoretical study of 10 wide band-gap semiconductor LSS host materials: traditional semiconductors GaN, SiC, and ZnO, both pristine and with various dopants and alloys, including ternary and quaternary materials MgZnO and InGaZnO. The objective of this study was to identify the wide bandgap hosts with the greatest promise for LSS devices and compare their performance with LT-GaAs. From this effort three materials, Fe:GaN, MgZnO and Te:ZnO, were identified as having great potential as LSS devices because of their band-gap coincidence with frequency multiplied Ti:Sapphire lasers, increased thermal conductivity and higher breakdown voltage compared to LT-GaAs, as well as picoseconds scale recombination times.