There are problems with just using a light, mostly it won't keep the eggs humid enough. The eggs also would need to be turned several times a day like the mother duck does. Also you need to keep the temperature in a certain range. Some people on this website have made home made incubators, I put in links to a couple of their pages. It's quite a project to make one of these and then to do everything right to get ducklings to hatch in them, but maybe you would be interested in trying.
https://www.backyardchickens.com/web/viewblog.php?id=1996-chic-chick-bator
https://www.backyardchickens.com/web/viewblog.php?id=16572-the-incubator-irator
https://www.backyardchickens.com/web/viewblog.php?id=1996-chic-chick-bator
https://www.backyardchickens.com/web/viewblog.php?id=16572-the-incubator-irator