NOVELTY - The method comprises forming a substrate (31) on a surface of a base (30), and depositing a group III-nitride layers on or above the substrate, where the group III-nitride layers are deposited using laser as excitation energy, and band gap values of the group III-nitride layers progressively increase in a direction away from the substrate. The aluminum oxide substrate is formed by hard-anodizing the aluminum base. A surface of the aluminum oxide substrate comprises a grain boundary having crystals with single orientation.    USE - The method is useful for making a solar cell (claimed) such as concentrated photovoltaic cell.    ADVANTAGE - The method is capable of effectively improving conversion efficiency, decreasing dimension and lowering overall system cost by using low temperature process.    DETAILED DESCRIPTION - The method comprises forming a substrate (31) on a surface of a base (30), and depositing a group III-nitride layers on or above the substrate, where the group III-nitride layers are deposited using laser as excitation energy, and band gap values of the group III-nitride layers progressively increase in a direction away from the substrate. The aluminum oxide substrate is formed by hard-anodizing the aluminum base. A surface of the aluminum oxide substrate comprises a grain boundary having crystals with single orientation. The method further comprises forming a buffer layer between the substrate and the group III-nitride layers. The group III-nitride layers comprise an indium nitride layer, an indium gallium nitride layer, indium aluminum gallium nitride layer and an aluminum nitride layer orderly deposited in a direction away from the substrate. The band gap values of the group III-nitride layers are 0.7-6.3 electron volt. The group III-nitride layers are deposited by chemical vapor deposition at a temperature of below 500 degrees C. The laser is used to perform pyrolytic to carry out thermochemical decomposition or to perform photolytic to carry out photochemical reaction. The group III-nitride layers are deposited by a physical vapor deposition and a pulsed laser deposition.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a method for making a solar cell.    Base (30)    Substrate. (31)