Defect-Mediated Degradation of Microelectronics in Radiation Environments

X-rays, gamma rays, and beams of energetic charged particles (electrons, protons, and heavy ions) can cause microelectronic devices to degrade or fail in space and terrestrial environments. All these forms of radiation generate electron-hole pairs, whose total accumulation in a device, known as total ionizing dose (TID), cause gradual alteration of device parameters such as threshold voltage and transconductance in metal-oxide-semiconductor field-effect transistors (MOSFETs) and high-electron-mobility transistors (HEMTs). In lab experiments, X-rays are often used, which do not carry sufficient momentum to displace atoms. Parametric changes are caused by the trapping of holes at pre-existing defects or by the activation of pre-existing hydrogen-passivated defects at the insulator/semiconductor interface via hole-mediated hydrogen release, hydrogen transport, and reaction processes. Measured threshold voltage shifts, transconductance degradation, and low-frequency 1/<i>f</i> noise, combined with density-functional-theory (DFT)-based quantum calculations have provided extensive understanding of these defect-mediated processes in Si-based MOSFETs, GaN-based HEMTs, and in devices based on graphene and other 2D materials that may lead to flexible electronics. <br/> <br/>Energetic charged particles with sufficient energy and momentum may also cause displacement damage. In particular, <i>single</i> heavy ions striking a device can cause degradation or instant failure. Examples of destructive single-event (SE) effects are SE gate rupture and SE burnout. In both cases, the device failure is attributed to the generation of large concentrations of electron-hole pairs and the concomitant formation of a highly conducting “electron-plasma wire” along the path of an ion strike in a region of high electric field. In power devices, degradation or failure is aided by the stored energy due to the high voltage and Joule heating due to the large current pulse. A role for lattice defects generated by the energetic ions (displacement damage) is not usually invoked to channel or enable this plasma wire, but experiments show that defects generated by the ion strike can sometimes play important roles in device degradation and/or failure. We have pursued extensive DFT calculations that enable us to make the case for the formation of a “vacancy nanowire” along the single ion-strike path that channels a persisting current (degradation) and ultimately a catastrophic current or exploding void growth (failure). Among prominent candidate materials for power devices, we find that the energetics of these processes make SiC the most resistant and <i>b</i>-Ga₂O₃ the least resistant to such degradation, while GaN and AlN are intermediate cases.