Getting a good night's sleep is important for both your physical and mental well being so it is good that you are addressing your sleep needs. It is normal for your body to start to wake up when exposed to sunlight but obviously sometimes this is not convenient to your schedule.
There are many things you can try to be able to sleep longer in the morning. The first is, as you suggested, a sleep mask which you put over your eyes to block out the light. Make sure you find one that is comfortable so that it does not keep you up during the night. Another option is to buy room darkening blinds or shades to block out the sun from all your windows. Also of importance is to try to go to bed and wake up at the same time everyday, even on weekends, so that your body becomes used to your sleep schedule.
It is important for you to see your primary care doctor
to address your sleep concerns. He or she will do a history and physical to rule out any potential other causes of insomnia
as well as discuss appropriate treatment.