ON THE RICHARDSON CONSTANT FOR ALUMINUM/GALLIUM ARSENIDE SCHOTTKY DIODES

Measurements have been made of the Richardson constant (A**) for Al/GaAs Schottky diodes in which the aluminum is deposited epitaxially by molecular beam epitaxy. These diodes are the nearest to ideal that have yet been reported. The value of (A**) for n-type GaAs, after allowing for the temperature variation of the barrier height and for the effect of tunnelling, was found to be (0.41 +/- 0.15) x 10(4) A m-2 K-2. This is much lower than the previously accepted value, and confirms the low value reported by Srivastava, Arora, and Guha. Since there is no possibility of an interfacial layer in our diodes, we believe the low value of A** to be an intrinsic property of the Al/GaAs interface. The value of A** for Al/p-GaAs was found to be (7.0 +/- 1.5) x 10(4) A m-2 K-2, which is lower than the theoretical value, though the discrepancy is not so large as for n-type GaAs. Because of the uncertainty in A**, values of barrier hights obtained from C-2 vs V plots are likely to be more reliable than those deduced from I/V characteristics.