InGaAs diodes using integrated technology for low-noise millimeter-terahertz receivers

InGaAs-based planar mixer diodes were developed and demonstrated in both discrete form and integrated with an antenna. The planar topology utilizes an airbridge structure to contact the anode and hence increases mechanical stability and reliability by eliminating the whisker contact used in conventionai mixers. The layer structures were grown in-house on an Metallorganic Vapor Phase Epitaxy system (MOVPE) on InP substrates. A novel airbridge process was developed which improved the isolation etch uniformity allowing greatly increased process controllability with greatly reduced breakage of the Schottky contacts; giving greater than 80% yield of 1 ;A platinum plating process was used to produce plated Pt Schottky anode contacts to the InGaAs mixer diodes. Diodes produced by this Pt plating process (plated diodes) were compared to those having Schottky contacts produced from E-beam evaporated Pt (evaporated diodes). The plated InGaAs diodes showed an improved ideality factor averaging 1.24 vs. 1.59 for the evaporated diodes. At 5 mA DC current, plated InGaAs diodes also showed an average of 5.5 dB less noise in the 10 Hz-lOO KHz frequency range. At 1.4 GHz and a DC current of 5 mA, plated InGaAs diodes showed an average noise temperature of 220 K vs. 360 K for the evaporated InGaAs diodes.;InGaAs mixer diodes integrated with antennae showed a best-case mixer diode double-sideband noise temperature of 200 K at 94 GHz, which is on par with those of conventional state-of-the-art GaAs Schottky diodes near this frequency. This InGaAs diode, however, achieved the 200K noise temperature under zero-biased operation with only 0.63 mW of LO power which is one-half to one-third that required by similar GaAs diodes. A subharmonically-pumped InGaAs diode pair with an integrated antenna showed a double-sideband noise temperature of 1059 K at an LO power of 1.6 mW at 180 GHz.;InGaAs and GaAs mixer diodes were theoretically compared via Monte Carlo simulation and the InGaAs diodes' lower electron scattering rates were found to give them a significantly lower noise temperature above 1 THz. Comparison of the Monte Carlo diode noise with that measured from similar real diodes showed the existence of a measurable noise source which is not due to hot electron effects or intervalley scattering.;InGaAs/InAlAs heterostructure varactor diodes (VHV's) were also investigated. The VHV's lower series resistance combined with its steeper C-V curves were found to produce a significantly higher efficiency of conversion of power from the fundamental drive to the second harmonic than that of a similar conventional Schottky diode.