I'm just so scared to raise it with him based on how he reacts
Oh, OP, this isn't normal. People who love us and make us very happy don't also scare us into silence. The two are not compatible.
I don't see a defensive person, I see a controlling person and red flags.
How would you react if you found out your DD thought you loved your mobile phone more than her and was afraid of your temper? I suspect you would be upset and concerned and immediately take steps to change your behaviour, reassure your DD, and make changes.
Now, how do you anticipate him reacting? I suspect you anticipate an explosion of rage, insults and name calling, recriminations and the blame being thrown around, accusations of lying, etc, etc.
Can you see that has nothing to do with being defensive? Defensive would be disbelief, denial, trying to come up with a more plausible explanation, and then reaching acceptance.
If his 6 year old child is scared of him, then something is seriously, seriously wrong. I'd be afraid of someone who lost the plot over minuscule things like that and I'm an adult. It seems designed to make people afraid to do anything he dislikes if you've seen how he reacts to minor irritations.
I can't give you advice on how to prevent him kicking off when you approach him with this, because his behaviour isn't about what you're saying or doing, it's about his need to be in control and powerful without anybody questioning or challenging his authority. I can't change that or provide the perfect words to stop him. You've probably found that yourself by now.
With a normal person, I'd approach it as "your DD was chatting to me earlier, and she told me something that was worrying her. I'm really glad she told me and I've tried to reassure her because I know it's not the case, but she said she was worried you were more interested in your phone than her. What do you think we can do to reassure her that's not the case?"
There are other things I might add or change depending on the situation. In a normal situation where her dad wasn't terrifying her by flying into rages I might have thought it was in part down to her feeling vulnerable and uncertain about her family changing. In this situation it sounds like she's probably spot on. If he loved her he'd care that he was frightening her and he'd be listening to her mother's concerns and yours. But he's not. He doesn't seem to care at all. (Does he listen to anybody?)
His reaction will tell you everything. If he won't take this on board, that's not about you or how you approached him, that's about him. At some point you'll have to stop making excuses for his rages and his dominating behaviour.