Key factors in the preparation of low resistance ohmic contacts to p-GaN

Low resistance ohmic contacts to p-GaN are essential for the realization of GaN-based optoelectronic devices such as white light emitting diodes(LED's) with large power.However,the difficulty in achieving reliable low contact resistivity on p-GaN has affected seriously the output power and thermal stability of such devices.In this paper,key factors(e.g.surface treatment,choice of electrode materials and thickness,thermal annealing) in making low resistance ohmic contacts to p-GaN are discussed.The latest research progresses in this area are classified and some novel research ideas are put forwarded by us.