DEEP-LEVEL STATES IN MOVPE ALGAAS - THE INFLUENCE OF CARRIER GAS

We have studied the deep-level state content in AlGaAs grown by low-pr essure 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 ap parent 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 e xhibit a lower total concentration of deep-level states as well as net residual doping concentration N-D - N-A. These results favour nitroge n as the carrier gas over hydrogen in the MOVPE process. Finally, we f ound 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.