TEMPERATURE-DEPENDENT TRANSPORT-PROPERTIES OF N(+) GAAS LOW-TEMPERATURE GAAS/N(+) GAAS STRUCTURES GROWN BY MOLECULAR-BEAM EPITAXY/

The temperature-dependent I-V characteristics of n(+) GaAs low-tempera ture GaAs(AlGaAs) n(+) GaAs structures in which the low-temperature la yers were grown at 250, 350, and 450 degrees C were analyzed. Band con duction with an activation energy of 0.72 eV dominates at T>250 K. Hop ping conduction dominates at T<250 K, where the resistivity was found to be insensitive to temperature. From this analysis, it is shown that Fermi level is pinned to an acceptorlike deep level of about 10(17) c m(-3), which lies at 0.72 eV below the conduction band. Measured capac itance can be described in terms of a parallel-plate capacitance with separation being equal to the expected growth thickness. Majority trap s (electrons) were observed by deep-level transient spectroscopy with an activation energy about 0.72 eV, confirming the result of the resis tivity analysis. In addition, the I-V characteristics were fitted to t he simulated curves based on a simplified space-charge limited theory and the result was found to be consistent with the resistivity analysi s. (C) 1996 American Institute of Physics.