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

The dependence of Zn concentration, N-Zn, upon Zn partial pressure, P-Zn, h as been measured in InP and In0.53Ga0.47As after organometallic vapor phase epitaxial growth and compared with the equilibrium Zn solubility under com parable conditions. It was found that the Zn concentration incorporated dur ing growth of In0.53Ga0.47As follows the equilibrium solubility, i.e. N-Zn proportional to P-Zn(1/2). However, it was found that the Zn concentration incorporated during growth of InP deviated from equilibrium, i.e. N-Zn prop ortional to P-Zn was measured, similar to what has been previously reported for GaAs. For both InP and In0.53Ga0.47As, the maximum Zn concentration wa s found to be consistent with previously measured Zn solubility limits. Fro m these results, we conclude that at T = 600 degrees C, (1) the Fermi energ y at the surface of the InP is pinned below the intrinsic Fermi energy at a value of approximately E-i - E-f approximate to 0.35 eV, i.e. E-f is only modestly above the valence band edge, and (2) pinning of the Fermi energy a t the surface of In0.53Ga0.47As could not be measured. (C) 1999 Elsevier Sc ience S.A. All rights reserved.