Crystal orientation effects on electronic properties of wurtzite GaN/AlGaN quantum wells with spontaneous and piezoelectric polarization

Crystal orientation effects on electronic properties of a WZ GaN/AlGaN quantum well (QW) with spontaneous (SP) and piezoelectric (PZ) polarization are invetigated using the multiband effective-mass theory. The interband transition energy for the flat-band (FB) model without SP and PZ polarization shows a slow decrease with increasing crystal angle. On the other hand, the self-consistent (SC) model shows a significant redshift for cystal angles near theta = 0 and a rapid increase of the interband transition energy due to the reduced SP and PZ ploarization effects. The SC model also shows that the matrix elements are significantly reduced near the (0001) orientation due to the large spatial separation between electron and hole wave functions. However, it is observed that the matrix elements rapidly increase with crystal orientation. In the case of the average hole effective mass, both SC and FB models show that their effective mass is significantly reduced near the (10 (1) over bar 0) crystal orientation. These results mean that the non-(0001) QWs, particularly the (10 (1) over bar 0) QWs, have a much smaller effective mass and larger matrix elements compared to those of the conventional (0001)-oriented QW.