Nanometer-scale test of the Tung model of Schottky-barrier height inhomogeneity
Tung has shown [Phys. Rev. B 45, 13509 (1992)] that a range of 'nonideal' behaviors observed in metal/semiconductor (MS) Schottky diodes could be quantitatively explained by assuming that specific microscopic distributions of nanometer-sized 'patches' of reduced barrier height exist at the MS interface. Here we report a simultaneous microscopic and macroscopic test of this model as applied to metal/6H-SiC Schottky diodes, by (1) measuring the nm-scale barrier-height distribution (BHD) of particular Schottky diodes using ultrahigh vacuum (UHV) ballistic electron emission microscopy (BEEM), (2) extending the Tung model to calculate the expected nm-scale BHD for particular parameter values, and (3) quantitatively relating the measured nm-scale BHD of a particular Schottky diode to its macroscopic I-V characteristic. Our studies indicate that (1) for relatively ideal diodes, both the microscopic and macroscopic behaviors are explained well by the Tung model with a large coverage (>5%) of shallow patches, (2) the measured BHDs are nearly identical for relatively ideal and highly nonideal diodes, and (3) a simple Tung model can account for highly nonideal behavior only by assuming an unphysical patch distribution in which the excess current is dominated by a few patches in the extreme tail of the patch distribution. Our measurements instead suggest that all the diodes contain a broad 'intrinsic' distribution of shallow patches, while the large excess current in highly nonideal diodes is due to a few large defects of extrinsic origin. This last conclusion is consistent with a recent study by Skromme and co-workers [J. Electron. Mater. 29, 376 (2000)].
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40230860
- Journal Information:
- Physical Review B, Vol. 64, Issue 7; Other Information: DOI: 10.1103/PhysRevB.64.075310; Othernumber: PRBMDO000064000007075310000001; 074128PRB; PBD: 15 Aug 2001; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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