P. Altuntas

Power Performance at 40 GHz of AlGaN/GaN High-Electron Mobility Transistors Grown by Molecular Beam Epitaxy on Si(111) Substrate

This letter reports on the demonstration of microwave power performance at 40 GHz on AlGaN/GaN high-electron mobility transistor grown on silicon (111) substrate by molecular beam epitaxy. A maximum dc current density of 1.1 A· mm-1 and a peak extrinsic transconductance of 374 mS · mm-1 are obtained for 75-nm gate length device. At VDS = 25 V, continuous-wave output power density of 2.7 W · mm-1 is achieved at 40 GHz associated with 12.5% power-added efficiency and a linear power gain (G p) of 6.5 dB. The device exhibits an intrinsic current gain cutoff frequency FT of 116 GHz and a maximum oscillation frequency FMAX of 150 GHz. This performance demonstrates the capability of low cost microwave power devices up to Ka-band.

First Power Performance Demonstration of Flexible AlGaN/GaN High Electron Mobility Transistor

This letter reports on the first demonstration of microwave power performance at 10 GHz on flexible AlGaN/GaN high-electron-mobility transistor (HEMT). A maximum dc current density of 620 mA/mm at VGS = 0 V and a peak extrinsic transconductance of 293 mS/mm are obtained for a 2 × 50 × 0.1 μm2 flexible device. At VDS = 5 V, a continuous-wave saturation output power density of 0.42 W/mm is achieved at 10 GHz, and associated with a maximum power-added efficiency of 29.8% and a linear power gain of 15.8 dB. The device exhibits an intrinsic current gain cutoff frequency FT of 38 GHz and a maximum oscillation frequency FMAX of 75 GHz. This result demonstrates the capability of flexible GaN-based HEMT for the development of applications requiring mechanical flexibility, high frequency operation, as well as high power performance.

Impact of the Bending on the Electroluminescence of Flexible InGaN/GaN Light-Emitting Diodes

The role that the mother substrate plays to influence the performance of InGaN/GaN-based light-emitting diodes (LEDs) onto the adhesive flexible tapes is addressed in this letter. For this purpose, the electroluminescent (EL) spectra and current density-voltage (J-V) characteristics of flexi-LEDs are studied under different convex bending configurations (from a curvature radius of infinity to 1.4 cm), showing only one peak around 442 nm in all the cases. Both the EL spectra and J-V characteristics are affected by the applied tensile stress when the flexi-LED is bent. In fact, an increase of the applied tensile strain from 0.02% to 0.09% results in a red-shift of the EL peak energy by 3 meV at 0.7 mA, and a drop of the current at high forward bias. In addition, such flexi-LEDs exhibit a reversible response when a significant mechanical deformation is applied.

Electron delay analysis and image charge effect in AlGaN/GaN HEMT on silicon substrate

A delay time analysis is carried out for SiN-passivated AlGaN/GaN High Electron Mobility Transistors (HEMTs) on silicon substrate featuring gate length of 90 nm. The influence of high parasitics in the access pads is considered using de-embedding procedure from the measured S parameters. From the obtained transit delay contributions, the effective electron velocity is estimated to 0.85×107 cm.s-1. In addition, the effect of the image charge on the drain delay is experimentally demonstrated through the extraction of the mirroring coefficient a close to the predicted simulation value.