Cree does publish some SPICE models - for the XP-G, XP-G2, XP-E, XP-E2, XM-L, XB-D and probably others. Those are the ones I've used in LTSPICE.
Here's an example. Starting at the Cree.com home page, click on these:
Components and Modules
Document Library
On the documents page, look up...