High Mg effective incorporation in Al-rich Al( x )Ga(1 - x )N by periodic repetition of ultimate V/III ratio conditions

According to first-principles calculations, the solubility of Mg as a substitute for Ga or Al in Al( x )Ga(1 – x )N bulk is limited by large, positive formation enthalpies. In contrast to the bulk case, the formation enthalpies become negative on Al( x )Ga(1 – x )N surface. In addition, the N-rich growth atmosphere can also be favorable to Mg incorporation on the surface by changing the chemical potentials. On the basis of these special features, we proposed a modified surface engineering technique that applies periodical interruptions under an ultimate V/III ratio condition (extremely N-rich), to enhance Mg effective incorporation. By optimizing the interruption conditions (2 nm interruption interval with 2 s interruption time), the enhancement ratio can be up to about 5 in the Al(0.99)Ga(0.01)N epilayer.