AB-INITIO CALCULATIONS OF SECOND ORDER OPTICAL RESPONSE FUNCTIONS IN WURTZITE GAN AND ALN, AND THEIR SHORT PERIOD SUPERLATTICES

摘要

Second harmonic generation coefficients were calculated from first-principles for wurtzite GaN, AlN and the (0001) superlattices (SL) (GaN)_n(AlN)_n for n = 2,4. The effects of the LDA gap underestimate are discussed. The SLs are found to have a strongly reduced static SHG response. The frequency dependent SHG coefficients are found to be sensitive to the SL band structure and to differ significantly form a superposition of the bulk components, indicating a strong intermixing of the bands.