Can I pray tahajjud with only sura Fatiha, and sura Ikhlas?

I'm confused about the exact procedure of this prayer. I read in some places that there is no mandatory rules for tahajjud, and found somewhere that in every rakat we can recite sura Fatiha then 3 times sura Ikhlas. and can repeat the same in every rakat. I was doing so always. But now read somewhere that our Prophet read surah from quran (ex: sura Bakara etc), which are very long, and I wasn't able to memorize these. In this circumstances, can I pray tahajjud with only sura Fariha, and sura Ikhlas? That is easier for me.