Add columns in SharePoint list error with special characters

Question

It throws error when I try to create and add column in list which contains special characters such as '&'.

I tried following:

DisplayName="a&b" Name="a&b" -------- throws error

DisplayName="a&amp ;b" Name="a&amp ;b" -------- throws error (remove space before';')

DisplayName="a&amp ;b" Name="a_x0026_b" -------- works fine (remove space before';')

Do I really need to convert special characters to their respective special codes for example '&' to 'x0026' ?

Is there any official document saying that ?

function addFields() {

        var clientContext = new SP.ClientContext.get_current();
        var oWebsite = clientContext.get_web();
        //Getting reference to the list
        oList = clientContext.get_web().get_lists().getByTitle('List1');


        var f2 = clientContext.castTo(
                    oList.get_fields().addFieldAsXml('<Field Type="Choice"  DisplayName="a&amp;b" Name="a&amp;b" />', true, 
                    SP.AddFieldOptions.addToDefaultContentType),
                    SP.FieldChoice);
        var choices = Array("Approved", "Rejected", "Progress");
        f2.set_choices(choices);
        f2.update();

        clientContext.executeQueryAsync(
            Function.createDelegate(this, this.onQuerySucceeded),
            Function.createDelegate(this, this.onQueryFailed)
            );
    }

    function onQuerySucceeded() {
        alert("List Field Updated");
    }

    function onQueryFailed(sender, args) {
        alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
    }


addFields()