Residual donors and acceptors in high-purity GaAs and InP grown by hydride VPE

Residual donors and acceptors in epitaxial films of GaAs and InP grown by the hydride vapor phase epitaxy technique were investigated using the complementary techniques of photothermal ionization spectroscopy and variabletemperature photoluminescence. High-purity samples of GaAs grown in three different laboratories were compared and high-purity InP samples were also measured. The dominant shallow acceptors in the GaAs samples were found to be C and Zn, and deep Cu and Mn acceptors were also observed. The donors Si, S, and Ge were observed in the GaAs with S being dominant. A clear correlation was observed between the gas phase stoichiometry during growth and the relative incorporation of column IV donors (Si and Ge) and column VI donors (S) in GaAs. Substrate quality, source purity, and atmospheric contamination of the growth system were found to influence the photoluminescence spectra of the GaAs samples. In the InP samples three shallow acceptors were observed including Zn, an unknown shallow acceptor level with E_A ≃ 21 meV, and an acceptor which may be either C or Mg. An unusual deep, structured emission band was also seen. The donors in the hydride InP were also found to be present in LPE InP and are believed to be Si and S.