The 18-year-old Germany youth international signed his first professional contract in mid-2012, and has made four league appearances, scoring in the 2-1 victory over Swansea City in September.
"He has technical ability, he has power, he has pace, he has finishing quality and he can give a final ball," Arsenal manager Arsene Wenger told the club's website (www.arsenal.com).
"He's a powerful offensive player and I believe that he will be a great player for Arsenal Football Club."
The length of the contract was not disclosed.
- Sports & Recreation