Investigation of Si and O Donor Impurities in Unintentionally Doped MBE-Grown GaN on SiC(0001) Substrate

• Published in: Journal of electronic materials Vol. 46; no. 8; pp. 4898 - 4902
• Main Authors: Tingberg, Tobias, Ive, Tommy, Larsson, Anders
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.08.2017; Springer Nature B.V
• Subjects: Atomic force microscopy; Carrier density; Characterization and Evaluation of Materials; Chemistry and Materials Science; Doping; Electrical resistivity; Electronics and Microelectronics; Epitaxial growth; gallium nitride; Impurities; Instrumentation; Lattice vacancies; Materials Science; Molecular beam epitaxy; N-vacancy; O donor; Optical and Electronic Materials; Plasmas (physics); Secondary ion mass spectroscopy; Si donor; Silicon carbide; Solid State Physics; Spectroscopic analysis; unintentional doping; Molecular beam epitaxy; N-vacancy; O donor; gallium nitride; unintentional doping; Si donor
• ISSN: 0361-5235; 1543-186X; 1543-186X
• DOI: 10.1007/s11664-017-5484-y

We have investigated the unintentional n -type background doping in GaN(0001) layers grown on semi-insulating 4H-SiC(0001) substrate by plasma-assisted molecular beam epitaxy under Ga-rich conditions at growth temperatures from 780°C and 900°C. All layers exhibited very smooth surface morphology with monolayer steps as revealed by atomic force microscopy. Hall-effect measurements showed that the sample grown at 900°C had carrier concentration of 9.8 × 10 17  cm −3 while the sample grown at 780°C had resistivity too high to obtain reliable measurements. Secondary-ion mass spectroscopy revealed O and Si concentrations of <10 17  cm −3 in the sample grown at 900°C but >10 17  cm −3 in the sample grown at 780°C. The trend for the atomic concentrations of O and Si, which are common donor impurities in GaN, was thus contrary to the trend of the carrier concentration. The full-width at half-maximum for x-ray rocking curves obtained across the GaN(0002) and GaN(10 1 ¯ 5) reflections for the sample grown at 900°C was 62 arcsec and 587 arcsec, respectively. The half-width increased with decreasing growth temperature. The atomic concentrations of O and Si are too low to account for the unintentional background doping levels. A possible explanation proposed in early reports for the background doping is N-vacancies.