Hi ajay, 

There are many number of ways to measure Dits. But the most simplest way is to extract Dit using Terman method or from conductance method from high frequency CV measurements. But the accuracy of Dits at band edges extracted from above methods are questionable. On the other hand TDRC measurements gives a better insigth to the interface traps along the bandgap.  But it all also depends on what structures you have as well?

you can fabricated single molecular layer FET, to study the interface directly, you can reffer to this article,http://www.sciencedirect.com/science/article/pii/S1566119914005072,     hope our work could offer you some help

Thank you so much Jiawae Wang, I will contact you If i have any doubt.....