Temperature-Independent Current Dispersion in 0.15 μm AlGaN/GaN HEMTs for 5G Applications

Thanks to high-current densities and cutoff frequencies, short-channel length AlGaN/GaN HEMTs are a promising technology solution for implementing RF power amplifiers in 5G front-end modules. These devices, however, might suffer from current collapse due to trapping effects, leading to compressed output power. Here, we investigate the trap dynamic response in 0.15 μm GaN HEMTs by means of pulsed I-V characterization and drain current transients (DCTs). Pulsed I-V curves reveal an almost absent gate-lag but significant current collapse when pulsing both gate and drain voltages. The thermally activated Arrhenius process (with EA ≈ 0.55 eV) observed during DCT measurements after a short trap-filling pulse (i.e., 1 μs) indicates that current collapse is induced by deep trap states associated with iron (Fe) doping present in the buffer. Interestingly, analogous DCT characterization carried out after a long trap-filling pulse (i.e., 100 s) revealed yet another process with time constants of about 1–2 s and which was approximately independent of temperature. We reproduced the experimentally observed results with two-dimensional device simulations by modeling the T-independent process as the charging of the interface between the passivation and the AlGaN barrier following electron injection from the gate

A memory window expression to evaluate the endurance of ferroelectric FETs

The recent discovery of ferroelectricity in HfO2 has revived the interest into non-volatile memories based on ferroelectric transistors (FeFETs). The key advantages of these FeFETs include the low power consumption and the compatibility with the existing CMOS process. On the other hand, issues related mainly to endurance still represent a challenge to the development of the technology. In this Letter, we propose to exploit an analytical expression for the Memory Window (MW) as a simple yet effective characterization tool to evaluate the endurance of FeFETs. The MW is defined as the difference between threshold voltages occurring due to polarization switching. The analytical formulation of the MW allows one to quickly estimate the generated trap concentration as a function of number of writing cycles (or time) without recurring to numerical simulations. With the aid of the analytical model, we find that for typical program/erase pulse amplitudes and duration, endurance has a weak dependence on writing conditions. The characterization technique based on the MW would allow the systematic comparison of the performance and endurance of next-generation FeFETs

La redazione dei protocolli notarili a Milano nel secolo XIV

Considerazioni di carattere diplomatistico sulle più antiche imbreviature notarili milanes

Il libello petitorio genovese: note diplomatistiche

Il saggio si concentra su di un tipo di atto, il così detto libello petitorio, offrendo alcune prime decisive delucidazioni in un campo lasciato a margine dai diplomatisti. Lo studio di questo contratto offre motivi di grande interesse sia per la particolare forma di convalidazione sia, nella prospettiva del suo sviluppo storico, per le insospettate conferme che offre all’interpretazione del travagliato momento in cui, intorno alla metà del secolo XII, definitivamente si impone la figura professionale del notai

Carta partita, sigillo, sottoscrizione nelle convenzioni della Repubblica di Genova nei secoli XII-XIII

Il contributo descrive l'evoluzione laboriosa delle forme di convalidazione nella documentazione genovese dei secoli XII-XII

Il libello petitorio genovese: note diplomatistiche

Il saggio si concentra su di un tipo di atto, il così detto libello petitorio, offrendo alcune prime decisive delucidazioni in un campo lasciato a margine dai diplomatisti. Lo studio di questo contratto offre motivi di grande interesse sia per la particolare forma di convalidazione sia, nella prospettiva del suo sviluppo storico, per le insospettate conferme che offre all’interpretazione del travagliato momento in cui, intorno alla metà del secolo XII, definitivamente si impone la figura professionale del notai

Turbulence structure of open channel flows over permeable and impermeable beds : A comparative study

Peer reviewedPublisher PD