2,600 research outputs found
Temperature and Chip Size Dependance of Carrier Recombination Dynamics and Droop Behavior on High Power COTS-LEDs
No full textReliability and instabilities in GaN-based HEMTs
No full textThis talk reviews the physical mechanisms that limit the performance and the reliability of GaN-based high electron mobility transistors (HEMTs), by comparing experimental data with the results presented in the literature. We discuss the following relevant aspects: (i) exposure to high electric field, in the off-state, may induce a significant trapping of charge within the device; this may induce an increase in the on-resistance, or a shift in the threshold voltage, that may negatively affect the performance of the devices; (ii) trapping may also be induced by the presence of hot electrons which, accelerated by the electric field, may achieve enough energy to be injected into the buffer and/or in the barrier layer; (iii) several mechanisms can be responsible for the degradation of GaN-based HEMTs: the generation of gate leakage paths, the generation of defects due to hot electrons, the delamination of the passivation, electrochemical reactions at the surface; (iv) the breakdown voltage of HEMTs is often lower that the theoretical value, due to a number of mechanisms, including the existence of punch-through current components, vertical drain-bulk leakage, and impact ionization
Reliability and high field related issues in GaN-HEMT devices; Part I
No full textIn recent years, the number of published research studies on GaN HEMT reliability has increased exponentially, extrapolated mean time to failure values in excess of 106 hours have been claimed; however, failure mechanisms remain partially unknown, making extrapolation (largely based on Arrhenius-like models) questionable. Identified failure mechanisms include time-dependent gate leakage increase during reverse bias tests, hot-electron-induced drain current degradation, gate and ohmic contact degradation, delamination of passivation, electron trapping.
This tutorial will present an overview of the main reliability issues in Gallium Nitride HEMTs, including a survey of DC and pulsed electrical characterization techniques, current collapse and other dispersion effects, accelerated testing methods and failure analysis. The effects of surface, interface and bulk traps will be discussed, on the basis of experimental data obtained by means of pulsed measurements, Deep Level Transient Spectroscopy, photocurrent spectroscopy and of 2D device simulation results. Failure modes and mechanisms of GaN HEMTs will be critically reviewed, on the basis of the experience gained within various European projects
EOS-related failures of modern high-brightness white LEDs: failure limits and correlation with device structure
No full textHot electrons and time-to-breakdown induced degradation in AlGaN/GaN HEMTs
No full textThis paper reports on the experimental evidences of
hot electrons induced degradations of AlGaN/GaN HEMTs
submitted to on-state stress tests. Thanks to the use of a
combined electrical and electroluminescence characterization we
demonstrate that: (a) exposure of devices to on-state stress can
induce a remarkable decrease in drain current; (b) drain current
degradation is due to electron trapping induced by hot electrons
in the gate-drain access region; (c) degradation rate strongly
depends on the intensity of the EL signal emitted by the devices
during stress, while it has a negligible dependence on
temperature. Finally, we derived an accelerated degradation law
for GaN HEMT submitted to accelerated bias test, by using the
intensity of the EL signal as a measure of the stress acceleration
factor
- …
