Abstract: 
GaN-based devices, due to the excellent electrical properties of gallium nitride and related materials, such as the high value of the critical electric field, wide bandgap, and high mobility and saturation velocity of two-dimensional electron gas carriers in AlGaN/GaN quantum wells, are widely used in high-power and high-frequency electronics. In this work we present the results of development of GaN-based transistor both for high power and microwave electronics carried out at Lukasiewicz Research Network-Institute of Microelectronics and Photonics. We have developed key technological steps i.e. regrown ohmic contacts for devices on bulk semi-insulating GaN substrates, selective etching of p-GaN layers over AlGaN, deposition of proper passivation layer as well as thermally stable isolation of adjacent devices using selective Fe+ ion implantation, which were integrated in the process flow of manufacturing of high power transistors. We have shown measurements of developed microwave transistors on bulk GaN substrates as well as normally-off p-GaN gate AlGaN/GaN HEMT power transistors assembled using in-house developed process in TO-220 package. Finally, ongoing works on development of vertical GaN power transistors will be presented.

Abstract: 
The important direction in Low Power research is associated with the usage of ferroelectric materials to obtain the negative differential capacitance. This talk discusses the development of capacitor models providing the analysis of ferroelectric circuits by SPICE-like simulator. The separate models for standalone capacitors are proposed, which are determined by the dependencies "charge on voltage and "voltage on charge". The equivalent nonsingular subcircuit is presented that provides the series connection of any number of nonlinear capacitors with floating nodes. The models take into account the trapped charges in floating nodes. The subcircuit for star connection of arbitrary capacitors is also described. The results of SPICE simulations of some ferroelectric circuit configurations are given to show the efficiency of the proposed approach.

Abstract: 
Recently flexible electronics has experienced tremendous advances, enabling the demonstration and sometimes also commercialization of foldable displays, conformable tags, and wearable monitoring systems. Besides sensors, actuators, and antennas, also flexible analog circuits allowing signal conditioning and communication are extremely needed. Among state-of-the-art technologies employing low-temperature processes, InGaZnO (IGZO) thin-film-transistors (TFTs) are especially suited to realize flexible analog circuits with good electrical and mechanical performance. Here, we report on the modelling, fabrication, and characterization of flexible IGZO TFTs and circuits. First, we show the DC and AC characteristics of devices fabricated on polyimide using Al2O3 insulators. Next, we present different approaches to reduce the TFT channel length (down to 160 nm), together with their influence on the AC performance. Best AC results are achieved for 500 nm-long self-aligned TFTs, yielding 135 MHz and 398 MHz transit and maximum oscillation frequencies, respectively. The applicability of such devices is then demonstrated in a broad range of fexible analog circuits, including different amplifiers and AM receivers/transceivers. Besides unipolar NMOS IGZO circuits, also CMOS amplifiers complementing IGZO with single-walled carbon nanotubes (SWCNTs) are also presented. Finally, we show how fully flexible sensor systems integrating magnetic sensors with IGZO operational amplifiers allow outperforming commercial rigid sensors.

Abstract: 
CMOS technology and electronics are rigid and bulky. Their applications are focused on computation-communication-infotainment. Scaling down their dimensions has been enabling their triumph. However, for wide deployment of electronics, their physically flexible version will be of great importance. Unfortunately material driven exploration of physically flexible electronics often compromise their data management efficiency. Therefore, we took a critical look at the data management efficiency of devices made with a variety of emerging and traditional materials. Our result clearly indicates that we need to compromise on achieving higher data performance with rigid materials. That necessitates a deeper and pragmatic look at how we can transform such rigid electronics into physically flexible one and integrate them seamlessly into ubiquitous electronic systems.