Nanometer high performance InP Schottky detectors are scaled to IR wavelengths. The increased cutoff frequency of the Schottky detector was accomplished by both reducing its capacitance to attofarad range and also by reducing the contact resistance. The Schottky detectors were fabricated on InGaAs/InP substrates with the doping level as high as 1 x 1019 cm-2. The typical Schottky detector anode size was 0.1 x 1 μm2. Planar broadband antennas were designed for LWIR wavelengths to couple the radiation into the nanometer size detector. Several different IR antenna designs were evaluated, including complimentary square spirals, bow ties and crossed dipoles. A 6 × 7 array of antenna-coupled Schottky detectors was characterized at DC, yielding a 20 KΩ zero-bias resistance and a responsivity of 6 A/W for the entire array. The arrays were characterized at 2.5 THz, as well as in the IR (3-5μm and 10.6 μm). The current results for polarization sensitivity confirm that an antenna-coupled mechanism is responsible for the measured responsivity with the highest value measured at the THz range.
We report experimental results for the optical responsivity and noise-equivalent power (NEP) of quasi-optically
coupled, room-temperature ErAs-InGaAlAs rectifier diodes. Four-micron-diameter diodes were flip-chip coupled to
self-complementary log-periodic and square-spiral antennas, and characterized with a 104-GHz Gunn diode oscillator
coupled to the rectifiers through variable attenuators, a feedhorn, an aspherical polymeric lens, and a Si
hyperhemisphere. The log-periodic mounted device displayed a responsivity and specific NEP' of 0.9x103 V/W and
1.2x10-12 W/Hz1/2, respectively. The square-spiral mounted device displayed a responsivity and NEP' of 1.2x103 V/W
and 2.0x10-12 W/Hz 1/2, respectively. All values were measured at a post-detection center frequency of 33 Hz.
We present the first mm-wave characterization of Semimetal Semiconductor Schottky (S3) diodes for direct detector applications from 94 GHz to 30 THz. The S3 devices use molecular-beam epitaxy growth of binary compounds that are closely lattice-matched and crystallographically perfect across the heterointerface to reduce 1/f and burst noise while maintaining ultra-high-frequency performance. The S3 diodes are fabricated from an InAlGaAs/InP based material system with both the Schottky layer and contact layer having n and n+ doping levels. The semimetal Schottky contact is ErAs which is grown in-situ during the MBE growth. By varying the InAlAs percentage content in the epitaxial layer structure, the diode dc I-V characteristics and its zero bias responsivity are optimized. Diode s-parameter data from dc-100 GHz is used to determine the diode responsivity as a function of frequency and diode capacitance and resistance. These measurements then allow the device intrinsic and extrinsic equivalent-circuit elements to be optimized for direct detection from 94 GHz to ~30 THz.
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