THE EFFECT OF GROWTH TEMPERATURE ON THE ELECTRICAL-PROPERTIES OF ALINAS/INP GROWN BY MOLECULAR-BEAM EPITAXY AND METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION

Al0.48In0.52As layers grown on n+-InP substrates by molecular beam epitaxy (MBE) and metal-organic chemical-vapor deposition (MOCVD), as a function,of substrate temperature, have been characterized by current-voltage-temperature, capacitance-voltage, deep-level transient spectroscopy, and admittance spectroscopy measurements. It was found that for diodes formed on MOCVD-AlInAs the current in forward bias is dominated by thermionic emission and the reverse current by recombination through the residual midgap states; whereas, for MBE-AlInAs diodes, the respective currents are dominated by defect-assisted tunneling at low forward and reverse biases. Schottky barrier heights were found to decrease with decreasing growth temperature. Three defect levels E1, E2, and E3 were observed in both material systems, and their densities were found to increase rapidly from approximately 10(12) to approximately 10(16) cm-3 as the growth temperature decreased from 740 to 500-degrees-C. The decrease of barrier height and the appearance of the defect-assisted tunneling current at low bias were found to correlate with the increase of defect density. The high density of defects may be responsible for the low barrier heights and higher leakage currents previously observed in AlInAs/InGaAs/InP high electron mobility transistors though MOCVD growth provided high quality AlInAs layers.