Effect of substrate temperature on migration of Si in planar-doped GaAs

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Abstract
Quantum oscillations in the magnetoresistance of GaAs δ (or planar) doped with Si are analyzed to obtain the electron densities of the electric subbands. We compare these densities with the results of self-consistently calculated subband structures of δ-doped GaAs in which the spread of the dopant atoms (Si) in the growth direction is a fitting parameter. The results indicate that there is negligible spread in structures grown at a substrate temperature TS ≲530 °C, while in structures grown at higher TS there is measurable spread which increases with TS. For TS =640 °C, the Si spread is determined to be ≂220 Å. An examination of the three-dimensional Si densities in these layers indicates that the dominant mechanism for the spreading of Si for TS >600 °C is the migration of Si to satisfy the solid solubility limit.