A fabrication technology of GaAs planar Schottky varactor diode （PSVD） is successfully developed and used to design and manufacture CaAs-based monolithic frequency multiplication based on 23-section nonlinear transmission lines （NLTLs） consisting of a coplanar waveguide transmission line and periodically distributed PSVDs. The throughout design and optimization procedure of 23-section monolithic NLTLs for frequency multiplication in the k-band range is based on a large signal equivalent model of PSVD extracted from small-signal S-parameter measurements. This paper reports that the distributed SPVD exhibits a capacitance ratio of 5.4, a normalized capacitance of 0.86 fF/μm2 and a breakdown voltage in excess of 22 V. The integrated 23-section NLTLs fed by 20-dBm input power demonstrates a 26-GHz peak second harmonic output power of 14-dBm with 25.3% conversion efficiency in the second harmonic output frequency range of 6 GHz-26 GHz.
A new PMMA/PMGI/ZEP520/PMGI four-layer resistor electron beam lithography technology is successfully developed and used to fabricate a 120 nm gate-length lattice-matched In_（0.53）Ga_（0.47）As/In_（0.52）Al_（0.48） As InP-based HEMT,of which the material structure is successfully designed and optimized by our group.A 980 nm ultra-wide T-gate head,which is nearly as wide as 8 times the gatefoot（120 nm）,is successfully obtained,and the excellent T-gate profile greatly reduces the parasitic resistance and capacitance effect and effectively enhances the RF performances. These fabricated devices demonstrate excellent DC and RF performances such as a maximum current gain frequency of 190 GHz and a unilateral power-gain gain frequency of 146 GHz.
A millimeter wave large-signal model of GaAs planar Schottky varactor diodes based on a physical analysis is presented.The model consists of nonlinear resistances and capacitances of the junction region and external parasitic parameters.By analyzing the characteristics of the diode under reverse and forward bias,an extraction procedure of all of the parameters is addressed.To validate the newly proposed model,the PSVDs were fabricated based on a planar process and were measured using an automatic network analyzer.Measurement shows that the model exactly represents the behavior of GaAs PSVDs under a wide bias condition from -10 to 0.6 V and for frequencies up to 40 GHz.
A broadband frequency doubler using left-handed nonlinear transmission lines（LH NLTLs） based on MMIC technology is reported for the first time.The second harmonic generation on LH NLTLs was analyzed theoretically. A four-section LH NLTL which has a layout of 5.4×0.8 mm^2 was fabricated on GaAs semi-insulating substrate. With 20-dBm input power,the doubler obtained 6.33 dBm peak output power at 26.8 GHz with 24-43 GHz—6 dBm bandwidth.The experimental results were quite consistent with the simulated results.The compactness and the broad band characteristics of the circuit make it well suit for GaAs RF/MMIC application.
120 nm gate-length In_（0.7）Ga_（0.3）As/In_（0.52）Al_（0.48） As InP-based high electron mobility transitions（HEMTs） are fabricated by a new T-shaped gate electron beam lithograph（EBL） technology,which is achieved by the use of a PMMA/PMGI/ZEP520/PMGI four-layer photoresistor stack.These devices also demonstrate excellent DC and RF characteristics：the transconductance,maximum saturation drain-to-source current,threshold voltage,maximum current gain frequency,and maximum power-gain cutoff frequency of InGaAs/InAlAs HEMTs is 520 mS/mm,446 mA/mm, -1.0 V,141 GHz and 120 GHz,respectively.The material structure and all the device fabrication technology in this work were developed by our group.
The left-handed nonlinear transmission line （LH-NLTL） based on monolithic microwave integrated circuit （MMIC） technology possesses significant advantages such as wide frequency band, high operating frequency, high conversion efficiency, and applications in millimeter and submillimeter wave frequency multiplier. The planar Schottky varactor diode （PSVD） is a major limitation to the performance of the LH-NLTL frequency multiplier as a nonlinear component. The design and the fabrication of the diode for such an application are presented. An accurate large-signal model of the diode is proposed. A 16 GHz-39,6 GHz LH NLTL frequency doubler using our large-signal model is reported for the first time. The measured maximum output powers of the 2nd harmonic are up to 8 dBm at 26.4 GHz, and above 0 dBm from 16 GHz to 39.6 GHz when the input power is 20 dBm. The application of the LH-NLTL frequency doubler furthermore validates the accuracy of the large-signal model of the PSVD.
GaAs-based planar Gunn diodes with A1GaAs hot electron injector have been successfully developed to be used as a local oscillator of 76 GHz in monolithic millimeter-wave integrated circuits. We designed two kinds of structure diode, one has a fixed distance between the anode and cathode, but has variational cathode area, the other has a fixed cathode area, but has different distances between two electrodes. The fabrication of Gunn diode is performed in accordance with the order of operations： cathode defining, mesa etching, anode defining, isolation, passivation, via hole and electroplating. A peak current density of 29.5 kA/cm^2 is obtained. And the charavteristics of negative differential resistance and the asymmetry of the current-voltage curve due to the A1GaAs hot electron injector are discussed in detail. It is demonstrated that the smaller size of active area corresponds to the smaller current, and the shorter distance between anode and cathode also corresponds to the lower threshold voltage and higher peak current, and hot electron injector can effectively enhance the radio frequency conversion efficiency and output power.
