Fallback for mathcal unicode characters in lualatex with proper height

I'm not seeing any OpenType font with the Computer Modern calligraphic letters. With Latin Modern Math you get a similar glyph. Anyway, I'm afraid you need to compute the scale factor yourself.

\documentclass{article}
\usepackage{fontspec}
\usepackage{newunicodechar}

\setmonofont{DejaVu Sans Mono}[Scale=MatchLowercase]
\newfontface{\calligraphic}{Latin Modern Math}[Scale=0.85]
\newunicodechar{}{{\normalfont\calligraphic }}

\begin{document}

Aa\texttt{AaA}

\end{document}