No
Positive and negative energy are not defined as either good or evil, although some of the uses of those energy sources may themselves be good or evil.
The Dungeon Master's GuideDungeon Master's Guide p. 43 states only this about the planes of positive and negative energy:
The Positive and Negative Planes. These two planes enfold the rest of the cosmology, providing the raw forces of life and death that underlie the rest of existence in the multiverse.
Player's HandbookPlayer's Handbook p.300 300 makes a similar statement:
Like a dome above other planes, the Positive Plane is the source of radiant energy and the raw life force that suffuses all living beings, from the puny to the sublimtsublime. Its dark reflection is the Negative Plane, the source of necrotic energy that destroys the living and animates the undead.
Negative energy is the source of energy that gives rise to undead creatures (DMG p.96 96). However, casting circle of death (PHB p.221 221), which conjures negative energy, is not described as an evil act.
Necromancy itself is not considered evil, as per PHB p.118 118:
Most people see necromancers ansas menacing, or even villainous, due to the close association with death. Not all necromancers are evil, but the forces they manipulate are considered taboo by many societies.
And on p.203 203 it is described that raising undead is not good, although this does not make a statement about negative energy itself:
Creating the undead through the use of necromancy spells such as animate dead is not a good act, and only evil creatures use such spells frequently
