Critical issues in Al Ga1−N growth

Strain and defects are the most serious issues for the growth of AlGaN. In situ stress monitoring revealed that tensile stress originating from the lattice mismatch between AlGaN and GaN is modulated by doping with Si or Mg. A low-temperature (LT) AlN interlayer between AlGaN and GaN is found to reduce tensile stress during growth, and suppress the propagation of dislocations which have screw components. However, additional pure edge dislocations are generated at the LT interlayer. In addition to the LT interlayer, a trenched structure was used for lateral growth, thereby achieving crack-free AlGaN with low dislocation density. AlGaN-based multi-quantum wells (QWs) have been fabricated on low-dislocation-density AlGaN, the photoluminescence (PL) efficiency of which is comparable to that of GaInN-based QWs.