  In the HEP-experiments of High Luminosity upgrade of the Large Hadron
Collider (HL-LHC), the application of isolation implants like $p$-stop between
$n^+$-electrodes of position sensitive $n$-on-$p$ sensors has been typically
considered to counter the detrimental effect on position resolution of the
accumulation of positive net oxide charge with radiation. In addition to the
positively charged layer close to the Si/SiO$_2$-interface, surface damage
introduced by radiation in SiO$_2$-passivated silicon particle detectors
includes the accumulation of trapped-oxide-charge and interface traps. A
previous study of either n/$\gamma$ (mixed field)- or $\gamma$-irradiated
Metal-Oxide-Semiconductor (MOS) capacitors showed evidence of substantially
higher introduction rates of acceptor- and donor-type deep interface traps
($N_\textrm{it,acc/don}$) in mixed-field environment. In this work, an
inter-electrode resistivity ($\rho_\textrm{int}$) TCAD-simulation study of
$n$-on-$p$ sensors with and without $p$-stop isolation implants was conducted
for both irradiation types. Higher levels of $\rho_\textrm{int}$ showed
correlation to higher densities of deep $N_\textrm{it,acc/don}$, with the
isolation performance of the mixed-field irradiated sensors becoming
independent of the presence of $p$-stop implant between the $n^+$-electrodes
throughout the investigated dose range up to about 100 kGy. The low
introduction rates of deep $N_\textrm{it,acc/don}$ in $\gamma$-irradiated
sensors resulted in high sensitivity of $\rho_\textrm{int}$ to the presence and
peak doping of $p$-stop above the lowest dose of 7 kGy in the study. Because of
the advantageous influence of radiation-induced accumulation of deep
$N_\textrm{it}$ on the inter-electrode isolation, position sensitive $n$-on-$p$
sensors without isolation implants may be considered for future HEP-experiments
where the radiation is largely due to hadrons.
