Sensitivity enhancement of metal-semiconductor-metal photodetectors on low-temperature-grown GaAs using alloyed contacts

in IEEE Photonics Technology Letters (2008), 20(12), 1054-1056

We have fabricated and characterized metal–semiconductor–metal (MSM) photodetectors based on lowtemperature-grown GaAs with alloyed (i.e., ohmic-type) contacts. The annealed contacts optimize the electric ... [more ▼]

We have fabricated and characterized metal–semiconductor–metal (MSM) photodetectors based on lowtemperature-grown GaAs with alloyed (i.e., ohmic-type) contacts. The annealed contacts optimize the electric field distribution inside the photodetector structure which results in an up-to-200% responsivity increase of the devices, compared to conventional MSM detectors with standard nonalloyed (Schottky-type) metallization fabricated on identical material. The improved MSM device with alloyed contacts shows more than three times larger output amplitude at illumination with a 100-fs Ti : sapphire laser, compared to the nonalloyed devices, without degradation of detector speed. [less ▲]

Photomixers fabricated on nitrogen-ion-implanted GaAs

in Applied Physics Letters (2005), 87(4), 41106-1-3

We report on fabrication and measurement of photomixers based on nitrogen-ion-implanted GaAs. We used energies of 500 keV, 700 keV, and 880 keV to implant N+ ions into GaAs substrates with an ion ... [more ▼]

We report on fabrication and measurement of photomixers based on nitrogen-ion-implanted GaAs. We used energies of 500 keV, 700 keV, and 880 keV to implant N+ ions into GaAs substrates with an ion concentration of 3 1012 cm−2. The resulting material exhibited 110 fs carrier lifetime due to implantation-induced defects. Our photomixers were fabricated as metal-semiconductor-metal devices, placed at the feed point of a broadband antenna. Optoelectronic measurements were performed in the wavelength range between 350 nm and 950 nm. In comparison to their counterparts photomixers fabricated on low-temperature-grown GaAs the N+-implanted GaAs photomixers exhibit improvements on both the output power and responsivity. A maximal responsivity of above 100 mA/W was achieved and we did not observe any dependence of the mixer cut-off frequency on the bias voltage. These characteristics make N+-implanted GaAs the material of choice for efficient optoelectronic photomixers. [less ▲]

Ultrafast Phenomena in Freestanding LT-GaAs Devices

in Acta Physica Polonica A (2005), VOL 107; PART 1

We report on the fabrication and high-frequency performance of our photodetectors and photomixers based on freestanding low-temperature-grown GaAs. The MBE-grown low-temperature GaAs layers are lifted ... [more ▼]

We report on the fabrication and high-frequency performance of our photodetectors and photomixers based on freestanding low-temperature-grown GaAs. The MBE-grown low-temperature GaAs layers are lifted from the native GaAs substrate and transferred on top of variety of host substrates. The freestanding devices exhibit breakdown electrical ¯elds above 200 kV/cm and dark currents below 3 £ 10¡7 A at 100 V bias. Device photoresponse shows 0.55 ps wide electrical transients with voltage amplitudes up to 1.3 V, measured using an electro-optical sampling technique with 100 fs wide laser pulses. Photomixing experiments at 460 GHz yield a 9 times higher output power for the freestanding device on Si/SiO2 host substrate compared to the native substrate. [less ▲]

Fabrication and performance of hybrid photoconductive devices based on freestanding LT-GaAs, Ultrafast Phenomena in Semiconductors and Nanostructure Materials VIII,

in Proceedings of SPIE (2004), 5353 (2004)

We report on fabrication and high-frequency performance of our photodetectors and photomixers based on freestanding low-temperature-grown GaAs (LT-GaAs). In our experiments, the LT-GaAs/AlAs bilayers were ... [more ▼]

We report on fabrication and high-frequency performance of our photodetectors and photomixers based on freestanding low-temperature-grown GaAs (LT-GaAs). In our experiments, the LT-GaAs/AlAs bilayers were grown on 2-inch diameter, semi-insulating GaAs wafers by a molecular beam epitaxy. Next, the bilayer was patterned to form 10 × 10 μm2 to 150 × 150 μm2 structures using photolithography and ion beam etching. The AlAs layer was then selectively etched in diluted HF solution, and the LT-GaAs device was lifted from its substrate and transferred on top of a variety of substrates including Si, MgO/YBaCuO, Al2O3, and a plastic foil. Following the transfer, metallic coplanar transmission lines were fabricated on top of the LT-GaAs structure, forming a metal semiconductor-metal photodetectors or photomixer structures. Our freestanding devices exhibited above 200 V breakdown voltages and dark currents at 100 V below 3×10-7 A. Device photoresponse was measured using an electro-optic sampling technique with 100-fs-wide laser pulses at wavelengths of 810 nm and 405 nm as the excitation source. For 810-nm excitation, we measured 0.55 ps-wide electrical transients with voltage amplitudes of up to 1.3 V. The signal amplitude was a linear function of the applied voltage bias, as well as a linear function of the laser excitation power, below well-defined saturation thresholds. Output power from the freestanding photomixers was measured with two beam laser illumination experimental setup. Reported fabrication technique is suitable for the LT-GaAs integration with a range of semiconducting, superconducting, and organic materials for high-frequency hybrid optoelectronic applications. [less ▲]

Freestanding LT GaAs as a subpicosecond photoconductive switch and high-voltage photomixer

in Abstract book of 4th Symposium on Non-Stoichiometric III-V Compounds (2002), Physik Mikrostrukturierter Halbleiter 27