Fermi level pinning in low-temperature molecular beam epitaxial GaAs

• Published in: Applied physics letters 1992-09, Vol.61 (13), p.1585-1587
• Main Authors: SHEN, H, RONG, F. C, LUX, R, PAMULAPATI, J, TAYSING-LARA, M, DUTTA, M, POINDEXTER, E. H, CALDERON, L, LU, Y
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states; Exact sciences and technology; Impurity and defect levels; Physics
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.107504

The Fermi level position in low temperature (LT) GaAs has been studied by photoreflectance (PR). By etching the LT-GaAs to a different thickness, we find the Fermi level in the as-grown as well as the annealed LT-GaAs is firmly pinned. The pinning position, however, occurs at different energies: 0.47 eV below the conduction band edge for the as-grown samples and 0.65 eV below the conduction band edge for the annealed samples. The pinning in the as-grown LT-GaAs is believed to be the result of a high degree of charge compensation by deep levels, while the pinning in the annealed LT-GaAs is due to the depletion of carriers by the Schottky barrier at the metallic As precipitates. From the measured Fermi level and ionization ratio of As antisites, the (0/+) donor level of the As antisite in LT-GaAs is, for the first time, determined at Ec−0.57 eV.