Heeghtening or Heightening: How To spell?

The word Heeghtening is misspelled against Heightening, which is present continuous of "Heighten"

Word contains consecutive vowels 'EI' in between alphabets h & ghtening is misspelled as 'EE'
Wrong Spelling:  h-ee-ghtening 
Correct Spelling:  h-ei-ghtening 
Find more wrongly spelled words of Heightening to spell it well.