Transit hotel or sleeping options at DEL airport?

Hello everyone,

What are options to sleep comfortably (comfortably - means on a bed, in a private room with low noise, not on chairs at public place) at DEL airport?
Is there a sleeping pods or room either at lounges or is there a transit hotel?

My wife's flight arrives at 9PM and outgoing flight is at 8AM. It is highly desirable to spend night at transit area without need to enter India because it would require visa.

Thanks.