MATERIAL PROPERTIES OF GaN FILMS WITH Ga- OR N- FACE POLARITY GROWN BY MBE ON A1_2O_3 (0001) SUBSTRATES UNDER DIFFERENT GROWTH CONDITIONS

摘要

The marerial properties of GaN films grown on A1_2O_3 (0001) substrate nitridated at high and low temperatures were investigated. The effects of GaN or A1N nucleation layers and different III/V flux ratio on the polarity of the films were also investigated Reflected high energy electron diffraction (RHEED) was used for in-situ monitoring of the surface structure and films polarity. The optoelectronic properties were determined by low and room temperature photoluminescence measurements. Finally a method combining etching in a KOH solution and atomic force microscopy (AFM) was developed to indentify the polarity of the GaN films.