Metal-p(+)-n enhanced Schottky barriers on (100) InP formed by an open tube diffusion technique.

Rapid thermal processing has been utilized for shallow diffusions from ZnF(2)/SiO(2'), ZnF(2)/Al(2)O(3'), or CdF(2)/SiO(2) structures to increase the effective barrier height of Au- (100) n-InP Schottky diodes. For diffusion from a ZnF(2)/SiO(2) structure, an increase in apparent barrier height of 0.2-0.34eV with a reduction in reverse leakage of two orders of magnitude is obtained. High apparent barriers are also observed using ZnF(2)/Al(2)O(3) but in general the electrical characteristics are poor. Near-ideal characteristics are observed for diffusion from CdF(2)/SiO(2) layers, yielding a 0.11eV barrier increase and a reduction in reverse current by a factor of =60. This corresponds to a p(+) layer width of =120angstroms and an acceptor to bulk donor ratio N(A)/N(D)=150. However, degradation of the electrical characteristics due to dopantsubstrate reactions limits the enhancement attainable with the CdF(2) source. Methods for avoiding this problem with similar structures are proposed. A nonthermionic current component is observed for large barrier enhancements (>0.1eV) causing the reverse current to saturate at a value larger than expected from the apparent barrier height determined by the forward current-voltage characteristics. Possible origins for this excess current are discussed.