Is there a way to create a binary tree in Erlang using processes?

I am trying to create a binary tree using processes.

-module(binarytree).

-export([start/1, loop/2]).

start(N) ->
    P = spawn(?MODULE, loop, [N, self(), self(), self()]),
    P ! create_nodes,
    receive
    end.

loop(0, _, _, _) ->
    done;

loop(N, Root, LeftNode, RightNode) ->
    receive
        create_nodes ->
            MyPid = self(),
            LeftNode = spawn(?MODULE, loop, [N-1, MyPid, ???, ???]),
            RightNode = spawn(?MODULE, loop, [N-1, MyPid, ???, ???]),
            LeftNode ! create_nodes,
            RightNode ! create_nodes;
        _ ->
            ok
    end,
    loop(N, Root, LeftNode, RightNode).

Without LeftNode and RightNode I am creating tree structure successfully, but I want to save LeftNode and RightNode in loop's state. What should I pass in function arguments when creating nodes?

Update: Thanks to Nalin Ranjan. Change these lines:

MyPid = self(),
LeftNode = spawn(?MODULE, loop, [N-1, MyPid, ???, ???]),
RightNode = spawn(?MODULE, loop, [N-1, MyPid, ???, ???]),
LeftNode ! create_nodes,
RightNode ! create_nodes;

To:

MyPid = self(),
NewLeftNode = spawn(?MODULE, loop, [N-1, MyPid, "", ""]),
NewRightNode = spawn(?MODULE, loop, [N-1, MyPid, "", ""]),
NewLeftNode ! create_nodes,
NewRightNode ! create_nodes,
loop(N, Root, NewLeftNode, NewRightNode);

loop(N, Root, LeftNode, RightNode) -> 
 receive 
  create_nodes -> 
    MyPid = self(),
    NewLeftNode = spawn(?MODULE, loop, [N-1, MyPid, "empty-child-node", "empty-child-node"),
    NewRightNode = spawn(?MODULE, loop, [N-1, MyPid, "empty-child-node", "empty-child-node"]), 
    NewLeftNode ! create_nodes, 
    NewRightNode ! create_nodes, 
    loop(N, Root, NewLeftNode, NewRightNode); 

  _ -> ok 
end, 
loop(N, Root, LeftNode, RightNode). 

Try this one out.