Getting NULL value in Controller Object while passing POST Object using Jquery Ajax

I am trying to post html form data to .net core Controller Using Ajax Post. I am storing form data inside a Js Object and sending POST request to Controller using Ajax but I’m getting a null value int the controller object.

HTML Code

<div class="container">
    <form id="employeeForm">
        <div class="mb-3">
            <label asp-for="FullName" class="form-label">Full Name</label>
            <input type="text" asp-for="FullName" placeholder="Full Name" class="form-control" required>
            <input asp-for="Id" hidden />
        </div>
        <div class="mb-3">
            <label asp-for="Address" class="form-label">Address</label>
            <input type="text" asp-for="Address" placeholder="Address" class="form-control" required>
        </div>
        <div class="mb-3">
            <label asp-for="PhoneNo" class="form-label">Phone Number</label>
            <input type="text" asp-for="PhoneNo" placeholder="Phone Number" class="form-control" required>
        </div>
        <div class="mb-3">
            <label asp-for="Department" class="form-label"></label>
            <input type="text" asp-for="Department" placeholder="Department" class="form-control" required>
        </div>
        <div class="mb-3">
            <a class="btn btn-success" onclick="addEmployee()">Save</a>
            <a class="btn btn-danger" asp-controller="Home" asp-action="EmployeeList">Cancel</a>
        </div>
    </form>
</div>

JS Code

addEmployee = () => {
    if ($('#employeeForm').valid()) {
        
        var obj = {
            FullName: $('#FullName').val(),
            Address: $('#Address').val(),
            PhoneNo: $('#PhoneNo').val(),
            Department: 0
        }
        debugger;
        $.ajax({
            url: '/Home/AddEmployee',
            type: 'POST',
            contentType: 'application/xxx-www-form-urlencoded;charset=utf-8;',
            dataType: 'json',
            data: obj,
            success: function (res) {
                alert(res);
            },
        });
    }
   
};

C# Controller Code

public class Employee
{
    public int Id { get; set; }
    public string FullName { get; set; }
    public int Department { get; set; }
    public string Address { get; set; }
    public string PhoneNo { get; set; }
}

[HttpPost]
public JsonResult AddEmployee(Employee obj)
{
        return Json("hello");
}

Also, I have tried running it in debugging the post request send request to controller but with null data.