  Non-volatile memory (NVM) devices that reliably operate at temperatures above
300 $^\circ$C are currently non-existent and remains a critically unmet
challenge in the development of high-temperature (T) resilient electronics,
necessary for many emerging, complex computing and sensing in harsh
environments. Ferroelectric Al$_x$Sc$_{1-x}$N exhibits strong potential for
utilization in NVM devices operating at very high temperatures (> 500
$^\circ$C) given its stable and high remnant polarization (PR) above 100
$\mu$C/cm$^2$ with demonstrated ferroelectric transition temperature (TC) >
1000 $^\circ$C. Here, we demonstrate an Al$_{0.68}$Sc$_{0.32}$N ferroelectric
diode based NVM device that can reliably operate with clear ferroelectric
switching up to 600 $^\circ$C with distinguishable On and Off states. The
coercive field (EC) from the Pulsed I-V measurements is found to be -5.84 (EC-)
and +5.98 (EC+) (+/- 0.1) MV/cm at room temperature (RT) and found to decrease
with increasing temperature up to 600 $^\circ$C. The devices exhibit high
remnant polarizations (> 100 $\mu$C/cm$^2$) which are stable at high
temperatures. At 500 $^\circ$C, our devices show 1 million read cycles and
stable On-Off ratio above 1 for > 6 hours. Finally, the operating voltages of
our AlScN ferrodiodes are < 15 V at 600 $^\circ$C which is well matched and
compatible with Silicon Carbide (SiC) based high temperature logic technology,
thereby making our demonstration a major step towards commercialization of NVM
integrated high-T computers.
