Effect of the Al2O3 Interfacial Layer Thickness on the Measurement Temperature-Induced I-V Characteristics in Au/Ti Structures

Abstract

We prepared the Au/Ti/Al2O3/n-GaAs MIS (metal/insulating/semiconductor) structures with and without Al2O3 interfacial layer. The diode D1 has the interfacial layer thickness of 3 nm, and the diode D2 5 nm and diode D3 10 nm. We studied to obtain the high- or low-barrier-height devices depending on interfacial layer thickness for the availability of different opto-electronic circuit elements. We reported a zero-bias barrier height phi(b0) value of 0.77 eV for the as-deposited Au/Ti/n-type GaAs diode from the 300 K I-V measurements. We obtained the phi(b0) values of 0.73, 0.94, and 1.11 eV for the D1, D2, and D3 MIS diodes at 300 K, respectively. The temperature-induced current-voltage measurements for the diodes were made in the temperature range of 50-320 K. The phi(b0) value for the as-deposited and D1 diodes raised very slightly from 320 K down to 120 K, but it decreased sharply from 120 to 50 K. The temperature-induced current-voltage measurements for the diodes were made in the temperature range of 50-320 K. The phi(b0) value for the D2 and D3 diodes decreased slightly from 320 K down to 120 K, but it decreased sharply from 120 to 50 K. The apparent low barrier height (BH) with decreasing temperature can be attributed to the fact that the current preferentially flows through the low BH with the temperature due to the BH inhomogeneity. The R-s values for the as-deposited, D1, D2, and D3 MIS structures were determined as 130 omega, 5.80 omega, 101 omega, and 216 omega from the forward bias I-V curves at 300 K, respectively. The fact that the D1 and D2 samples have lower R-s values than that of the as-deposited sample may be attributed to the fact that the Al2O3 thin film improves the inhomogeneity of the Schottky interface.