Fabrication of magnesium-doped gallium nitride nanorods and microphotoluminescence characteristics

High density magnesium (Mg)-doped gallium nitride (GaN) nanorods were fabricated by inductively coupled plasma reactive ion etching technique from the epitaxial film. Under the fixed Cl2 Ar flow rate of 1025 SCCM (SCCM denotes cubic centimeter per minute at STP) and inductively coupled plasma/bias power of 200200 W, the nanorods were fabricated with a density of 108 - 1010 cm2 and dimension of 20-100 nm by varying the chamber pressure from 10 to 30 mTorr. A large blueshift was observed in the photoluminescence (PL) peak energy of Mg-doped GaN nanorods under HeCd laser (325 nm) excitation. The PL spectra of nanorods show a typical donor-acceptor-pair emission around 3.0 eV with a large blueshift compared to the Mg-doped GaN film. The blueshift energy increases from 8 to 67 meV as the excitation intensity varies from 12 to 56 kW cm2. Possible reasons causing the power dependence of spectral shift in the PL emission energy are discussed.