Nature of conventional current flow in a p-n junction
but when it comes to the n-side, involves &quot;movement&quot; of positive charge by positive ions?

Nope, for the most part, the positive ions in the n-side are the pos-charged dopant atoms, and those are locked into the crystal lattice.
It's confusing because there are actually four ions involved, not just two.
First, in the p-doped silicon, the neutral dopant atoms don't remain neutral.  Instead, a &quot;hole&quot; is created by each dopant atom, and it moves away.  This leaves the dopant atom with net negative charge.   Yet the wandering &quot;hole&quot; is actually a positively-ionized silicon atom!  At the same time, on average the entire hunk of p-type silicon has zero net-charge.  After all, every positive-charged hole has a negative-charged dopant ion somewhere nearby.  In other words, p-type silicon is actually made up of equal quantities of:

fixed negative-charged dopant ions
movable positive-charged silicon ions (the wandering &quot;holes.&quot;)


The n-type silicon is the opposite.  The dopant atoms in n-type silicon will contribute wandering electrons.  But when each electron initially leaves its dopant atom, that atom becomes a positive-charged ion.  And, when the wandering electron is sitting upon some distant silicon atom, that atom temporarily becomes a negative silicon ion.  So, n-type silicon is overall neutral, but is is composed of:

fixed positive-charged dopant ions
movable negative charged silicon ions (the mobile electrons.)


It gets worse!
Suppose that some holes wandered out of the p-side and invaded the n-type silicon?  Thermal motion causes them to jump around randomly, and the random jumping can take them over into the n-side.  They won't last long over there, but while they're briefly existing in the n-side, the holes are producing a region of positive net-charge!   (After all, they no longer are near their negative-charged dopant atoms, which were all left behind in the p-type side.)

but when it comes to the n-side, involves &quot;movement&quot; of positive charge by positive ions?

YES!  Because actually a &quot;hole&quot; is a positive-charged silicon ion  ...so if holes invade the n-side, electrically it's just as if some pos-charged silicon atoms were invading.   Yet the atoms themselves don't have to move.  Just their &quot;ionization&quot; is wandering around through the crystal.  (Heh, but at the same time, the n-side is full of positive-charged dopant ions which cannot move.  So, whenever n-type silicon is full of wandering holes, it actually contains two kinds of positive ions, but only one of them can move around.)
PS
Important question:  does p-type silicon have a positive charge?  Nope, since p-type silicon is full of non-movable negative dopant ions.  Their quantity is exactly the same as the quantity of wandering, positive-charged holes.  P-type silicon is a conductor of course, and that means we can give it a positive net-charge by hooking it to the positive terminal of a power supply.
And to make things even more interesting, if we connect p-type to n-type, some electrons will diffuse from n-type to p-type and become trapped in the depletion zone (because they encountered holes, and &quot;fell in.&quot;)  This causes the p-type side to become negative charged, and the n-type side to become equally positive.  This is the &quot;built-in potential&quot; of semiconductor junctions, which is caused by the &quot;built-in&quot; trapping of mobile charges in the depletion-zone.  Or in other words, a diode junction is also a spontaneously self-charged capacitor.