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),
        ),
      ],
    );
  };
}