Demonstration of THz Capability by MOCVD-grown Mixers and Varactors

Highlights of THz Diode Technology

• A novel planar technology InAlAs/InGaAs THz diode

• Maximum cutoff frequencies of InAlAs/InGaAs diodes.

• Demonstration of InP-based diodes using a novel planar airbridge technology with very short airbridges and no need for dielectric supported interconnects. A variety of InAlAs/InGaAs diodes were investigated to validate this technology.

• Demonstration of higher effective Schottky barrier and lower ideality factor for varactor diodes with thicker InAlAs barrier. Lowering of the InAs mole fraction in the barrier resulted in increased Schottky barrier but also higher ideality factor.

• Demonstration of reduced reverse saturation current for increased barrier thickness and In composition of InAlAs/InGaAs diodes. The results showed significant improvement over previously reported results for similar designs (Js,min~10^-4 A/cm^2 vs. 420A/cm^2).

• Demonstration of state-of-the-art zero bias cutoff frequency of 2.6THz with 1um diameter, 800 A i-InGaAs heteroepitaxial InAlAs/InGaAs diodes.

• Development of InP substrate removal technology and InAlAs/InGaAs diode lift off and mounting on glass or quartz substrates in order to dice and operate the devices in a ``parasitic-free'' environment.

• Demonstration of low-ideality factor diodes with low reverse leakage using InP/InGaAs diodes. A forward current of 1mA at 0.316V was found for these devices, indicating the need for much smaller bias than that required for comparable GaAs diodes. Suitability for mixer applications is thus suggested using InP/InGaAs designs.

• Demonstration of state-of-the-art noise performance by planar InGaAs mixer diodes using 2.4um diameter diodes. An SSB conversion loss of 6dB with a DSB noise temperature of 400K was obtained under optimum conditions of LO Drive (PLO=1.25mW) and Vbias=0.1V.

Technical Developments

Review of Group Activities