THERMAL-STABILITY OF EPITAXIAL ALUMINUM ON IN0.53AL0.47AS SCHOTTKY DIODES GROWN BY MOLECULAR-BEAM EPITAXY

Current-voltage and capacitance-voltage techniques have been used to c haracterize the electrical properties of annealed epitaxial aluminum c ontacts to In0.53Al0.47As grown by molecular beam epitaxy. These as-de posited diodes were found to have electrical characteristics that were dominated by thermionic emission, with an ideality factor of 1.06-1.0 8 and a barrier height of 0.55-0.56 eV. As the anneal temperature is i ncreased, there is a slight increase in the value of the barrier heigh t, which is believed to be related to an increasing interfacial reacti on occurring, promoting the formation of AlAs. For anneals above 400 d egrees C, the electrical characteristics start to degrade rapidly. For comparison, conventionally evaporated Au/InAlAs diodes were also char acterized. These diodes had an ideality factor of 1.14-1.18 and a barr ier height of 0.63-0.67 eV. Although the electrical characteristics sh owed little variation in the forward direction, the reverse characteri stics exhibited a significant variation between diodes. Upon annealing , the characteristics show variations between diodes, with the charact eristics significantly degraded for anneals of 300 degrees C, showing the poor thermal stability exhibited by conventionally evaporated cont acts. The observed characteristics for the epitaxial aluminum contacts to InAlAs, compared with those from conventionally evaporated gold co ntacts, have implications for the Schottky gate contact in the manufac ture of InAlAs-InGaAs high electron mobility transistors. (C) 1998 Ame rican Institute of Physics.