Comparison of excited nitrogen sources for molecular-beam-epitaxy GaN growth: Radio frequency and electron cyclotron resonance plasma sources

A comparative study of electron cyclotron resonance (ECR) and radio frequency (rf) plasma as a nitrogen source for molecular-beam epitaxy GaN was carried out. The effects of differences in the excited nitrogen species on the optical signals during GaN growth were investigated by 77 K photoluminescence (PL). For epitaxial layers grown at optimum V/III ratio using ECR and rf plasma, the PL spectra were dominated by near band-edge emission at 3.47 eV. However, when the V/III ratio was less than the optimum V/III ratio, a broad emission band at about 3.2-3.3 eV was observed in the PL spectrum for the GaN epilayer grown using rf plasma, while in the case of growth using ECR plasma, a deep level emission at about 2.2 eV appeared. These characteristics in PL spectra can used to identify differences in the chemical species in the nitrogen plasma. (C) 2000 American Institute of Physics. [S0003-6951(00)03926-7].