Interpretation of Capacitance-Voltage Profiles from Delta-Doped GaAs Grown by Molecular Beam Epitaxy

Abstract

Molecular beam epitaxy allows to grow narrow doping profiles which are described by the Dirac-delta function. Ionized impurities of delta(δ)-doped GaAs layers form a V-shaped potential well. Capacitance-voltage (C V) measurements on δ-doped GaAs with two-dimensional donor concentrations of N _D ^2D=4-6×10¹² cm^-2 performed at 77 and 300 K show a maximum C V-concentration of 6.8×10¹⁸ cm^-3 and a full-width at half-maximum of 46 Å, which does not depend on the sample temperature. A new theoretical model of C V-profiles from δ-doped GaAs is presented which takes into account the quantum-size effect. The quantum-mechanical interpretation of the C V-profiles shows that the measured profiles reflect neither the dopant concentration nor the free-carrier concentration. The C V-profiles reflect the shift of the electron wavefunction in the V-shaped potential well, which is tilted by the applied voltage. A good agreement between calculated and measured C V-profiles is found.