Flutter Icon Button with unwanted space around

I am still green in Flutter and is facing an IconButton spacing problem:

There is unwanted space around the icon. I didn't add any padding or sizedboxes between widgets, and I have the same problem with icons from awesome fonts also. Here is my code:

Widget contactCard(context, dl, i) {
  return GestureDetector(
    onTap: () {},
    child: Card(
      color: Colors.grey[300],
      child: SizedBox(
        height: 190,
        child: Padding(
          padding: EdgeInsets.all(10),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Text(dl[i].englishName, style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
              Text(dl[i].chineseName, style: TextStyle(fontSize: 14, fontWeight: FontWeight.bold)),
              constructPhone(dl[i].phone1),
              constructPhone(dl[i].phone2),
            ],
          ),
        ),
      ),
    ),
  );
}

Widget constructPhone(tel){
  if (tel.runes.length==0){
    return Text('');
  }else{
    return Row(
      children: [
        IconButton(
          padding: EdgeInsets.all(0),
          icon: const Icon(Icons.phone, size: 20),
          onPressed: () => launchUrl(Uri.parse("tel://" + tel)),
        ),
        Text(
          tel,
          style: TextStyle(fontSize: 18),
        ),
      ],
    );
  };
}

IconButton always have quite large paddings around them, to make it easier for users to tap on them.

If you don't want the padding, consider using Icon widget, and wrap it with GestureDetector to do your own onTap event. You can also consider making the whole row clickable (the icon, and the text) using GestureDetector or InkWell, to allow users to click on it easier.