  We demonstrate stable microresonator Kerr soliton frequency combs in a III-V
platform (AlGaAs on SiO$_2$) through quenching of thermorefractive effects by
cryogenic cooling to temperatures between 4~K and 20~K. This cooling reduces
the resonator's thermorefractive coefficient, whose room-temperature value is
an order of magnitude larger than that of other microcomb platforms like
Si$_3$N$_4$, SiO$_2$, and AlN, by more than two orders of magnitude, and makes
soliton states adiabatically accessible. Realizing such phase-stable soliton
operation is critical for applications that fully exploit the ultra-high
effective nonlinearity and high optical quality factors exhibited by this
platform.
