Zn solubility and Fermi energy pinning in InP and InGaAs: growth vs. equilibrium

The dependence of Zn concentration, NZn, upon Zn partial pressure, PZn, has been measured in InP and In0.53Ga0.47As after organometallic vapor phase epitaxial growth and compared with the equilibrium Zn solubility under comparable conditions. It was found that the Zn concentration incorporated during growth of In0.53Ga0.47As follows the equilibrium solubility, i.e. NZn∝PZn1/2. However, it was found that the Zn concentration incorporated during growth of InP deviated from equilibrium, i.e. NZn∝PZn was measured, similar to what has been previously reported for GaAs. For both InP and In0.53Ga0.47As, the maximum Zn concentration was found to be consistent with previously measured Zn solubility limits. From these results, we conclude that at T=600°C, (1) the Fermi energy at the surface of the InP is pinned below the intrinsic Fermi energy at a value of approximately Ei−Ef≈0.35 eV, i.e. Ef is only modestly above the valence band edge, and (2) pinning of the Fermi energy at the surface of In0.53Ga0.47As could not be measured.