Heterostructure Barrier Varactor Diodes Research Articles

Status and Prospects of High-Power Heterostructure Barrier Varactor Frequency Multipliers

There is a high demand for compact, room-temperature sources operating at millimeter-wave and terahertz (THz) frequencies for space instruments and terrestrial applications. This part of the electromagnetic spectrum is by far the least explored because of the difficulty of generating energy at these frequencies. Continuous-wave oscillators based on either electronics or photonics are limited in output power for fundamental reasons. Varistor and varactor frequency multipliers have shown outstanding performance in terms of output power, but further technical development will be essential to solve the lack of efficient and compact terahertz sources. In this paper, we present the status of heterostructure barrier varactor (HBV) diode frequency multipliers. The performance and prospects for THz applications in which HBV diode technology can offer advantages over conventional solutions are discussed. For instance, such a device can be easily scaled by increasing the number of barriers to produce and handle higher power. The inherent symmetry confines the power generation to odd harmonics, thereby simplifying the design of high-order frequency multipliers. For example, high-power triplers ( $\times 3$ ), quintuplers ( $\times 5$ ), nonlinear transmission lines (NLTLs) and grid multipliers utilizing HBV diodes are presented. Overall, HBV technology is a natural stepping stone from high-power microwave amplifiers to higher frequencies and can both simplify and improve the performance of terahertz sources.

Transfer of InP-based HBV epitaxy onto borosilicate glass substrate by anodic bonding

A new fabrication process is presented for epitaxial transfer of InP-based heterostructure barrier varactor diodes, as high-frequency varactor multipliers, onto low-dielectric borosilicate glass substrate, employing anodic bonding. The fabricated diodes on the new host substrate display symmetric electrical characteristics with only minor differences compared to those of the reference devices on the original InP substrate.

InAs-based heterostructure barrier varactor diodes with In0.3Al0.7As0.4Sb0.6 as the barrier material

InAs-based heterostructure barrier varactor (HBV) diodes with In0.3Al0.7As0.4Sb0.6 as the barrier material are demonstrated. Current–voltage and capacitance–voltage characteristics, as well as S-parameters, of HBV diodes with varying barrier thicknesses are examined. Maximum capacitance values and maximum-to-minimum capacitance ratios greater than those predicted by traditional HBV models were measured. The HBVs’ unconventional behavior in terms of charge accumulation layers adjacent to the wide bandgap barrier is discussed.

11% efficiency 100 GHz InP-based heterostructure barrier varactor quintupler

A record conversion efficiency of 11.4% at 100 GHz using a heterostructure barrier varactor (HBV) quintupler is demonstrated. The quintupler is based on a microstrip circuit mounted in a full-height crossed-waveguide block. The nonlinear element consists of a planar HBV diode fabricated in InGaAs/InAlAs/AlAs epitaxial layers on an InP substrate.

Heterostructure barrier varactors on copper substrate

The authors demonstrate a fabrication process where heterostructure barrier varactor diodes are fabricated on a copper substrate which offers reduced parasitic losses and improved thermal conductivity. This has been achieved without degrading the electrical characteristics.

Effects of self-heating on planar heterostructure barrier varactor diodes

The conversion efficiency for planar Al/sub 0.7/GaAs-GaAs heterostructure barrier varactor triplers is shown to be reduced from a theoretical efficiency of 10% to 3% due to self-heating. The reduction is in accordance with measurements on planar Al/sub 0.7/GaAs-GaAs heterostructure barrier varactor (HBV) triplers to 261 GHz at room temperature and with low temperature tripler measurements to 255 GHz. The delivered maximum output power at 261 GHz is 2.0 mW. Future HBV designs should carefully consider and reduce the device thermal resistance and parasitic series resistance. Optimization of the RF circuit for a 10 /spl mu/m diameter device yielded a delivered output power of 3.6 mW (2.5% conversion efficiency) at 234 GHz.