What is the piece of classical music at the end of "The Doors" movie and also on Jim Morrison's "An american Prayer"?

It's one of these three songs. All three were in the movie and on the album that you are referring to.

"The Movie"
Written by Jim Morrison
Performed by Jim Morrison

"Roadhouse Blues"
Written and Performed by The Doors
Elektra Records

"Ghost Song"
Written by Jim Morrison
Performed by The Doors

the piece of music is at the of the movie right after pam finds him in the tub,it is playing along with the poem "severed garden". and on American prayer album.it's a classical piece.

Albinoi Adagio

https://en.wikipedia.org/wiki/An_American_Prayer

Although not a classical aficionado but because of special memories attached to it I love this piece of music that has been used in several films (Rollerball, Gallipoli and Manchester by the sea and quite a few more). My ears pricked when I heard it at the end of "The Doors" and was surprised it was titled "severed garden" .
Wikipedia defines it this way:
The Adagio in G minor for violin, strings, and organ continuo is a neo-Baroque composition popularly attributed to the 18th-century Venetian master Tomaso Albinoni, but actually composed by 20th-century musicologist and Albinoni biographer Remo Giazotto, purportedly based on the discovery of a manuscript fragment by Albinoni. There is a continuing scholarly debate about whether the alleged fragment was real, or a musical hoax perpetrated by Giazotto, but there is no doubt about Giazotto's authorship of the remainder of the work.