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 temperature GaAs(AlGaAs) n⁺ GaAs structures in which the low-temperature layers were grown at 250, 350, and 450°C were analyzed. Band conduction with an activation energy of 0.72 eV dominates at T>250 K. Hopping 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 10¹⁷ cm^-3, which lies at 0.72 eV below the conduction band. Measured capacitance can be described in terms of a parallel-plate capacitance with separation being equal to the expected growth thickness. Majority traps (electrons) were observed by deep-level transient spectroscopy with an activation energy about 0.72 eV, confirming the result of the resistivity analysis. In addition, the I-V characteristics were fitted to the simulated curves based on a simplified space-charge limited theory and the result was found to be consistent with the resistivity analysis.