Hengshuang Zhang

A Scalable Active Compensatory Sub-Circuit for Accurate GaN HEMT Large Signal Models

A scalable active compensatory sub-circuit that focuses on and improves the accuracy of the GaN HEMT large signal model is proposed in this letter. Zero error between the simulated and measured dc I-V curves is obtained. Combining empirical and table-based models, time-consuming procedures for parameters extraction and optimizing can be simplified. With a normalizing factor introduced, the scaling of the model is accomplished. The validity of the proposed model is investigated experimentally. This model can be applied for devices with different designs and technology.

Substrate Integrated Waveguide Structural Transmission Line and Filter on Silicon Carbide Substrate

Substrate integrated waveguide (SIW) structural transmission line (TL) and filter are designed and fabricated on semi-insulating silicon carbide (SiC) substrates for operation at the low end of

Recessed-gate quasi-enhancement-mode AlGaN/GaN high electron mobility transistors with oxygen plasma treatment*

H

X-band inverse class-F GaN internally-matched power amplifier*

-band. The via-holes as the sidewall of SIW are achieved by using a fine dry-etching technique, where the radius and the via–via distance of the via-hole row are determined according to the transmission characteristics and the fabrication process. Measurements show that SIW-based TLs have the attenuation constant of as low as 0.45 dB/mm at 220 GHz, a third of that for TLs on grounded coplanar waveguide, and SIW-structural filters have the minimum insertion loss of <1 dB at the center frequency of 183 GHz with a bandwidth of 5.3 %. It illustrates the availability of passive device fabrications on SiC substrate, and paves the way for the forthcoming terahertz monolithic integrated circuits based on wide bandgap semiconductors.

Enhanced g m and f T With High Johnson’s Figure-of-Merit in Thin Barrier AlGaN/GaN HEMTs by TiN-Based Source Contact Ledge

In this paper, the enhancement-mode AlGaN/GaN HEMT combined with the low damage recessed-gate etching and the optimized oxygen plasma treatment was fabricated. Scanning electron microscope/energy dispersive spectrometer (SEM/EDS) method and x-ray photoelectron spectroscopy (XPS) method were used to confirm the formation of oxides. Based on the experimental results, the obtained enhancement-mode HEMT exhibited a threshold voltage of 0.5 V, a high peak transconductance of 210 mS/mm, and a maximum drain current of 610 mA/mm at the gate bias of 4 V. Meanwhile, the on/off current ratio of enhancement-mode HEMT was as high as 108, drain induced barrier lowering (DIBL) was as low as 5 mV/V, and subthreshold swing (SS) of 80 mV/decade was obtained. Compared with the conventional HEMT, the Schottky reverse current of enhancement-mode HEMT was three orders of magnitude lower, and the off-state breakdown voltage of which was higher. In addition, a power gain cutoff frequency (f max) of the enhancement-mode HEMT was larger than that of the conventional one.

Investigation of enhancement-mode AlGaN/GaN nanowire channel high-electron-mobility transistor with oxygen-containing plasma treatment

An X-band inverse class-F power amplifier is realized by a 1-mm AlGaN/GaN high electron mobility transistor (HEMT). The intrinsic and parasitic components inside the transistor, especially output capacitor Cds, influence the harmonic impedance heavily at the X-band, so compensation design is used for meeting the harmonic condition of inverse class-F on the current source plane. Experiment results show that, in the continuous-wave mode, the power amplifier achieves 61.7% power added efficiency (PAE), which is 16.3% higher than the class-AB power amplifier realized by the same kind of HEMT. To the best of our knowledge, this is the first inverse class-F GaN internally-matched power amplifier, and the PAE is quite high at the X-band.