研究目的

Investigating the high-frequency performance and temperature stability of zero-bias GaAsSb/InAlAs/InGaAs tunnel diodes for millimeter-wave detection in the 220–330-GHz band.

研究成果

We characterized GaAsSb/InAlAs/GaInAs tunnel diodes for zero-bias detection in 220–330-GHz frequency band. The nonlinear resistance of the diode at zero-bias produces the square-law rectification of the input signal. The diode with 0.8 × 0.8 μm2 mesa size achieved the sensitivity above 1000 V/W that was limited by the series resistance RS = 130 Ω and the junction capacitance CJ = 3.8 fF. The cutoff frequency was fC = (2π RSC J )?1 = 322 GHz. The devices demonstrated the enhanced temperature stability compared with zero-bias Schottky barrier diodes. The expected variations of the sensitivity over the temperature range from 17 to 300 K were SV (17 K)/SV (300 K) < 1.7 dB.

研究不足

The noise of the detector is limited by the thermal noise in the junction resistance RJ = 8 MΩ. At T = 300 K the RMS noise voltage per square root of a unit bandwidth is VN = (4 k B T RJ )1/2 = 0.37 μV/Hz1/2, which corresponds to noise equivalent power NEP = 370 pW/Hz1/2 for a given voltage sensitivity SV = 1 mV/mW. This value is a factor of 20 higher than the NEP of the Schottky diode reported in [11]. To improve the NEP the junction resistance RJ can be reduced by changing the thickness of the InAlAs barrier.