I'm thinking about how my friendships have naturally evolved in the past and will suggest doing those same things that got me my current friends.
If you've talked and done group activities quite a bit, then you must have some kind of idea of what his interests are. Does he like movies, food, music, games? If he loves burgers then suggest you two go to a great burger joint you know. If he likes games, suggest you check out the local vintage game shop or maybe play a game online together. Hopefully you get the idea. There's no one single activity that's good to propose, but if you suggest something you know you both enjoy, they're more likely to agree and it's less likely to seem weird.
Another option is to invite him to a group event, but with a different group of people than your academic group. That way you get a chance to get to know each other better and outside of your normal environment, but it's less intimate and therefore less intimidating for everyone involved. Once you've spent some time together like that, it'll seem more natural to do something one-on-one.
I'd definitely suggest you start with an activity that's either in public or in a group or both. Inviting someone to your house when it's just the two of you and you've never hung out in a personal setting before will be too big of a jump for most people. A gathering at your house with a bunch of people is fine.
Another thing you can do is suggest you swap personal phone numbers so you can share pictures of some common interest. For instance, I like going to renaissance faires, and they are excellent picture opportunities. You could easily have multiple conversations prompted by the crazy pictures I take there! So if you or he has an interest like that, that would be an opportunity to naturally deepen the relationship.
Caution: Don't say you just want their number to text them one picture and then randomly text about other things. I'm not suggesting a ruse to get their number dishonestly, as that will backfire. But if you naturally have something to text about (or Snapchat or whatever you happen to both use), then suggest you do so.
I can't promise he won't think you're weird for suggesting an activity, but you won't know until you try, and I promise the worst that will happen if you ask is that he'll say no.
One last thing: If it's possible this suggestion will be taken as a sign of romantic interest and that's not what you want, then be explicit about that. It's okay to say something like, "I love burgers too! There's an amazing spot near my place, and I'd love to take you this weekend if you're free. Just as friends, of course!" It'll avoid any awkward misunderstandings.