S.B.
That doesn't sound like enough sleep for a 3 yr old - although some kids just do not need as much sleep and others are naturally early risers. A couple of things to try:
1. Try moving up his nap time to earlier in the day.
2. Make sure that his room is completely dark, even when the sun starts coming up. It seems like his waking is around the same time as the start of sunrise. Is there a window in his room that the sunlight is peeking through first thing in the morning? Remember, 3 yr olds cannot tell time yet so often they think that daylight = waking up.
Good luck!