The fabrication and performance of planar doped barrier diodes as 200 GHz subharmonically pumped mixers

• Published in: IEEE transactions on microwave theory and techniques 1994-04, Vol.42 (4), p.742-749
• Main Authors: Trong-Huang Lee, East, J.R., Chen-Yu Chi, Rebeiz, G.M., Dengler, R.J., Mehdi, I., Siegel, P.H., Haddad, G.I.
• Format: Article
• Language: English
• Subjects: Acoustical engineering; Current measurement; Diodes; Doping; Fabrication; Gallium arsenide; Loss measurement; Noise measurement; Temperature; Voltage
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/22.285089

The PDB (planar doped barrier) diode consists of a p/sup +/ doping spike between two intrinsic layers and n/sup +/ ohmic contacts. Such devices can have an anti-symmetric current vs. voltage characteristic. The capacitance is approximately constant with the applied voltage, and the barrier height and device capacitance are easily adjustable. These characteristics make the PDB a candidate for millimeter- and submillimeter-wave subharmonic mixers. We have fabricated 2 and 4 /spl mu/m diameter diodes with different barrier designs using GaAs epi-layers. The devices are planarized using an air-bridge and a surface channel etch. After completely removing the substrate, the devices are mounted on a quartz substrate to reduce parasitic effects. Diced diodes were tested as subharmonic mixers around 200 GHz in both a quasi-optical planar wideband subharmonic receiver and a planar-diode waveguide-mixer. The quasi-optical measurements show that a 0.23 V (and 0.4 V) barrier height GaAs diode with 2.0 /spl mu/A (and 5 nA) of saturation current gives a DSB conversion loss of 10.8 dB (and 9.5 dB) and a DSB noise temperature of 3795/spl deg/ K and 2450/spl deg/ K). The waveguide mixer measurements were made with a similar 0.23 V barrier height PDB. Such a mixer has a minimum conversion loss of 10.2 dB and noise temperature of 3570/spl deg/ K, and requires only 1.2 milliwatts of available LO power.< >