ELECTRICAL CHARACTERISTICS OF LOW TEMPERATURE-AL0.3GA0.7AS

In this work, we present electrical characterizations of n(+) GaAs/low temperature (LT)-Al0.3Ga0.7As/n(+) GaAs resistor structures in which the LT layers are grown at nominal substrate temperatures of 250 and 300 degrees C. The resistivity and V-tfl parameters of these LT-Al0.3Ga0.7As layers are compared with those of LT-GaAs and Al0.3Ga0.7As grown at a normal growth temperature of 720 degrees C. Low-temperature Al0.3Ga0.7As layers exhibit resistivities as high as 10(12) ohm-cm, nearly four orders of magnitude higher than that of LT-GaAs, and V-tfl values as high as 45 V, over twice that of LT-GaAs. We also find that the LT-Al0.3Ga0.7As materials grown at 250 and 300 degrees C appear to show opposite and contradictory trends with respect to resistivity and V-tfl. We propose that this result can be explained by residual. hopping conduction in the 250 degrees C material. Temperature dependent conductivity measurements confirm the presence of a hopping mechanism in LT-Al0.3Ga0.7As grown at 250 degrees C and yield activation energies of 0.77 and 0.95 eV for LT-GaAs and LT-Al0.3Ga0.7As, respectively.