Was Lewis Carroll inspired by hallucinations during a fever to write Alice in Wonderland?

No, he wasn't.

Alice in Wonderland was influenced by numerous things. One was a girl named Alice LidDELL, who was the daughter of one of Lewis' acquaintances. Lewis told her stories and had a relationship which to this day is still question.

He made up Alice in Wonderland to entertain Alice and her sisters during a rowing trip, so we can assume the he was in full control of his faculties at the time, as it is unlikely that he would be so reckless as to take a group of children boating whilst feverish or suffering hallucinations.

Carroll's character in Alice in Wonderland was named after LidDELL and the story was edited by him later on, when he was preparing the story for publication.

There is no evidence at all that he suffered hallucinations, either self inflicted or due to illness, at any stage during the writing process.