Open external link on ion-tab

I have no idea how to open an external browser for the app. I already fixed it under <ion-item>, it works fine

<ion-item class="item-icon-right" id="boironMedicineFinder2-list-item1368" href-inappbrowser="https://www.boironusa.com/medicines/" onClick="openExternal(this)">Boiron Shop
      <i class="icon ion-ios-cart-outline"></i>
</ion-item> 

However, when I put <ion-tab>, it does not work

<ion-tab class="item-icon-right" id="boironMedicineFinder2-list-item1368" href-inappbrowser="https://www.boironusa.com/medicines/" onClick="openExternal(this)">Boiron Shop
      <i class="icon ion-ios-cart-outline"></i>
</ion-tab> 

Does anyone have any ideas to work for <ion-tab>? Thanks!