high technology vs high tech

high technology and high tech both are nouns.

Word	Noun	Adjective	Verb	Adverb
high technology	Yes	No	No	No
high tech	Yes	No	No	No

As nouns, high technology and high tech are synonyms defined as:

high technology and high tech: highly advanced technological development (especially in electronics)

high technology (noun)	high tech (noun)
highly advanced technological development (especially in electronics)	highly advanced technological development (especially in electronics)