Gaussian distribution of inhomogeneous barrier height in Al0.24Ga0.76As/GaAs structures

Current–voltage (I–V) characteristics of Al0.24Ga0.76As/GaAs structures have been investigated in the temperature range of 79–400 K. The barrier height ΦB, ideality factor n and density of interface states Nss determined from the forward bias I–V characteristics were found strongly depend on temperature. While the n and Nss decrease, the zero-bias barrier height ΦB0 increases with increasing temperature. This behavior has been interpreted by the assumption of a Gaussian distribution (GD) of barrier heights (BHs) due to the barrier inhomogeneities that prevail at the metal–semiconductor interface. A ΦB0 versus q/2kT   plot was drawn to obtain evidence of GD of BH, and values of Φ¯B0=0.788eV and σ0=0.091 V for the mean BH and zero-bias standard deviation have been obtained from this plot, respectively. Furthermore, the mean values of BHΦ¯B0 and the effective Richardson constant A* were obtained as 0.804 eV and 15.8 A/cm2 K2, which is close to the theoretical value of 8 A/cm2 K2, respectively, by means of the modified Richardson plot, ln(I0/T2)−q2σ02/2(kT)2 versus q/kT plot. Experimental results show that Al0.24Ga0.76As/GaAs structures have a good rectifying behavior and the temperature dependence of forward bias I–V characteristics of the Schottky barrier diode (SBD) have been successfully explained based on TE theory with GD of BHs. In addition, the Nss was determined from the forward bias I–V characteristics by taking into account the bias dependence of the effective BH.