Front passenger brake creaks while stopping

Creaking sound emanates from the front passenger side when braking. Doesn't become apparent until 40 or so MPH as it corresponds to the velocity of the wheel. Approaching a stop, the creaking sound gets louder and "slower." Took the wheel off and there is decent pad left. Noticed there's a very slight ridge in the rotor - thought it was this until I found out it doesn't do it in reverse. Older threads talked about creaking being related to a sticky caliper - could this be it even though it doesn't happen in reverse?