BIAS DEPENDENCE OF SCHOTTKY-BARRIER HEIGHT IN GAAS FROM INTERNAL PHOTOEMISSION AND CURRENT-VOLTAGE CHARACTERISTICS

Bias dependence of Schottky barrier height phi(B) was directly measured using an internal photoemission effect in Au-n-GaAs Schottky barrier diodes under both the forward and reverse applied voltages. Phi(B) increased by about 0.015-0.016 eV as the forward bias increased from 0 to 0.3 V. This is probably due to an applied-voltage-induced change in electron population in the interface states. The results were compared with the bias dependence derived from dark forward current-voltage (I-V) characteristics. Both bias dependences were in good agreement, indicating that nonideal forward I-V characteristics (a deviation from the ideal thermionic emission theory) could be fully explained by the bias dependence of phi(B) for diodes of a relatively good quality (an ideality factor, n=1.02-1.07). The effective Richardson constant A** was calculated to be about 1.3-1.4 X 10(5) A K-2 m-2 for the diodes of the lower n values using the value of the measured Schottky barrier height at zero bias. These values of A** were higher than the calculated value of about 8 X 10(4) A K-2 m-2 and that of 0.41 +/- 0.15 X 10(4) A K-2 m-2 reported by Missous and Rhoderick [J. Appl. Phys. 69, 7142 (1991)]. This is probably due to an enhancement of an electron tunneling through the high density interface states in our case. Phi(B) decreased by about 0.05-0.06 eV when the reverse voltage increased from 0 to 3.0 V. An image force lowering effect could not account for this large reverse bias dependence of the barrier height. The nonideal reverse I-V characteristics could not be interpreted solely by the bias dependence of phi(B). This discrepancy was attributed to other leakage current mechanisms.