Evaluation of carrier concentration reduction in GaN-on-GaN wafers by Raman spectroscopy and Kelvin force microscopy

• Published in: Japanese Journal of Applied Physics Vol. 56; no. 8S1; pp. 8 - 12
• Main Authors: Yamamoto, Hidekazu, Agui, Kazuya, Uchida, Yuhki, Mochizuki, Shota, Uruma, Takeshi, Satoh, Nobuo, Hashizume, Tamotsu
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Society of Applied Physics 01-08-2017; Japanese Journal of Applied Physics
• Subjects: Carrier density; Coupled modes; Diffusion layers; Dopants; Electronic devices; Epitaxial growth; Gallium nitrides; Metalorganic chemical vapor deposition; Microscopy; Organic chemicals; Organic chemistry; Raman spectra; Raman spectroscopy; Silicon; Spectrum analysis; Substrates; Vapor phase epitaxy; Vapor phases; Wafers
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.56.08LB07

The carrier concentration in a gallium nitride (GaN) substrate of a GaN-on-GaN wafer grown by hydride vapor phase epitaxy (HVPE) was evaluated by Raman spectroscopy and Kelvin probe force microscopy (KFM). On the basis of the longitudinal optical phonon-plasmon coupled (LOPC) mode of Raman spectra and surface potential measurements by KFM, the carrier concentration at the periphery of the HVPE-GaN substrate was found to be about one order of magnitude lower than that at the center. The decrease in carrier concentration is considered to be due to the out-diffusion of dopants during the metal organic chemical vapor deposition (MOCVD) of the epitaxial layer. In silicon (Si) epitaxial wafers, the autodoping of out-diffused dopants introduces nonuniform device characteristics. This undesirable effect needs to be suppressed to successfully move from prototype GaN-on-GaN power devices to commercial products.