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Much attention has been paid to the photoresponse of vanaduim oxide (VOx) and amorphous silicon based microbolometer for long-wavelength infrared detection under un-cooled operation condition in recent decades. However, the outstanding physical and chemical properties of graphene and reduced graphene oxide (rGO) stimulate their potential for use in light-sensitive applications. Much less attention has been paid to investigate the performance on long-wavelength infrared detection of microbolometer using reduced graphene oxide/SiNx/vanadium oxide composite films deposited on under room temperature operation. In the research, we have proposed the novel microbolometer based on VOx/SiNx/rGO composite films replace the as-deposited VOx based microbolometer. It is noted that such extraordinary properties (high responsivity: 18,130 V/W and low NETD: 43.32 mK) of the VOx/SiNx/rGO composite presented here encourage us to contemplate on this protocol for next generation optoelectronic device engineering for infrared detection.

Field-plate (FP) multigate AlGaN/GaN high electron mobility transistor (HEMT) single-pole–single-throw (SPST) radio-frequency (RF) switches were implemented and studied by performing low-frequency noise measurements for high power switch operations. The measured harmonic power suppression results and low frequency noise spectra of various FP multigate devices were analyzed. The parameters of an OFF-state (gate bias = −5 V) small-signal model were individually extracted for FP single-, dual-, triple-, and quadruple-gate switch devices. Under ON-state (gate-bias = 0 V) operation, the insertion loss performance was slightly low because of the increase in the gate number and ON-state resistance (RON). However, the second and third harmonic suppression ratios were enhanced by 6.5 and 11 dBc, respectively, from the single-gate device to the quadruple-gate device. The current noise power spectral density measured as a function of the gate overdrive voltage for various devices at 77–300 K also indicated that the FP gate achieved a low surface trap density, which is beneficial for harmonic power suppression in high power applications.

The thermal stability and reliability of AlGaN/GaN high electron mobility transistors (HEMTs) on Si substrates with a 2-μm thick copper interconnection (Cu-INTC) were evaluated. The use of metallic copper as a conducting metal has the advantages of higher thermal conductivity, low cost and low sheet resistance. For comparison, traditional gold metal interconnection (Au-INTC) devices were fabricated under the same process conditions. Thermal infrared (IR) microscopy measurements show that the Cu-INTC devices could function at a lower channel temperature (TCHANNEL) than traditional Au-INTC devices with the same drain current density, because of the low resistivity of the metal. The typical peak transconductance (gm), output power (POUT), power gain (Gp) and power-added-efficiency (PAE) during operation at 100 °C were 87.53 mS/mm, 22.85 dBm, 11.1 dB and 25.9% for a Cu-INTC power device with gate width of 1 mm and these measured results were better than those of Au-INTC devices. They indicate that the copper metal provides great potential for high-power AlGaN/GaN HEMT applications.

Gate structure of AlGaN/GaN metal–oxide–semiconductor high electron mobility transistors (MOS-HEMTs) on silicon substrates has been developed using electron-beam evaporated high-permittivity (high-k) zirconium oxide layer (ZrO2). As a gate insulator, this structure has been investigated and compared with the conventional GaN HEMTs. From the measured capacitance–voltage (C–V) curve, the dielectric constant of ZrO2 was 20.7 and the voltage shift of C–V hysteresis phenomena can be reduced to 7.2 mV after high temperatures annealing. The crystalline structures of ZrO2 at different annealing temperatures were observed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The ZrO2 thin film achieved a better thermal stability after high temperatures annealing. Moreover, the MOS-HEMTs with ZrO2 gate insulator layer markedly improved its gate leakage current and microwave performances. The device linearity was also improved due to its flat and wide transconductance (gm) distribution which was analyzed by polynomial curve fitting technique. Load–pull and flicker noise measurements showed that ZrO2 MOS-HEMT had a higher output power at high input swing and low surface density. Therefore, ZrO2 was a potential candidate high-k material for the gate insulator on GaN-based MOS-HEMT for it exhibited a better thermal stability and reliability at high power applications.