A thermal expansion interface between silicon (Si) and gallium nitride (GaN) films using multiple buffer layers of aluminum compounds has been provided, along with an associated fabrication method. The method provides a (111) Si substrate and deposits a first layer of AlN overlying the substrate by heating the substrate to a relatively high temperature of 1000 to 1200° C. A second layer of AlN is deposited overlying the first layer of AlN at a lower temperature of 500 to 800° C. A third layer of AlN is deposited overlying the second layer of AlN by heating the substrate to the higher temperature range. Then, a grading Al1-XGaXN layer is formed overlying the third layer of AlN, where 0