Unintentional doping of a-plane GaN by insertion of in situ SiN masks

H Witte (1) , M Wieneke (1) , A Rohrbeck (1) , K -M Guenther (1) , A Dadgar (1) , A Krost (1)

1 Institute of Experimental Physics

Undoped a-plane GaN layers grown by metal organic vapor phase epitaxy on sapphire (10-12) substrates using low temperature GaN seed layers and in-situ SiN masks were characterized by Hall-effect measurements, CV-characteristics and photovoltage spectroscopy. With increasing deposition time of the SiN masks the electron concentrations of the GaN layers are enhanced. The dominant activation energy between 14 meV and 22 meV determined by temperature dependent Hall-effect is very similar to the donor silicon on gallium site. Two other activation energies at 30 meV and between 50 meV and 70 meV were found corresponding well with O Ga and V N defects, respectively. The depth profiles of the net donor densities show a strong increase towards the substrate /LT-GaN/HT-GaN interface indicating diffusion of silicon from the SiN mask towards the surface. Therefore, the Si-doping is attributed to the dissolution of the SiN masks during the following high temperature GaN layer growth. Sidoping from the SiN masks also explains the deterioration of the band bending within the LT-GaN / HT-GaN junction found by photovoltage spectroscopy.

Mots clés: Physical Sciences

H Witte, M Wieneke, A Rohrbeck, K -M Guenther, A Dadgar, et al.. Unintentional doping of a-plane GaN by insertion of in situ SiN masks. Journal of Physics D: Applied Physics, 2011, 44 (8), pp.85102. ⟨10.1088/0022-3727/44/8/085102⟩. ⟨hal-00629982⟩