Deep-level states in MOVPE AlGaAs: the influence of carrier gas

We have studied the deep-level state content in AlGaAs grown by low-pressure metalorganic vapour-phase epitaxy with nitrogen and hydrogen as the carrier gases at various growth temperatures. Layers grown in the Nz and H(2) ambients contain the same type of donor-like traps with apparent activation energies 0.34, 0.56 and 0.89 eV, besides the 1.03 eV trap unique for the former layer. Moreover, the layers grown in N(2) exhibit a lower total concentration of deep-level states as well as net residual doping concentration N(D) - N(A). These results favour nitrogen as the carrier gas over hydrogen in the MOVPE process. Finally, we found out that increasing the temperature of epitaxial growth gradually reduces the gain observed for the carrier gas N(2). (C) 1998 Elsevier Science B.V. All rights reserved.