You can do it using a WakeLock
this way:
When you set your notification:
WakeLock screenOn = ((PowerManager)getSystemService(POWER_SERVICE)).newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP, "example");
screenOn.acquire();
And, IMPORTANT, release the wakelock when you don't need it anymore:
screenOn.release();