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Absence of Evidence for Fixed Charge in Metal–Aluminum Oxide–Silicon Tunnel Diodes
Author(s) -
Marstell Roderick J.,
Pugliese Anthony,
Strandwitz Nicholas C.
Publication year - 2019
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201800342
Subject(s) - diode , materials science , schottky diode , aluminium , dipole , silicon , oxide , schottky barrier , optoelectronics , semiconductor , doping , condensed matter physics , insulator (electricity) , composite material , metallurgy , chemistry , physics , organic chemistry
Here, a controlled variation in the fixed charge density ( N F ) and thickness of aluminum oxide tunnel insulators is reported, and the impact on Schottky barrier height ( Φ B ) in metal–insulator–semiconductor (MIS) diodes is studied. Analysis of metal–aluminum oxide–silicon capacitor structures indicates a change in N F from +1 × 10 12 cm −2 in as‐deposited films to −2 × 10 12 cm −2 in annealed films. An analytical model and numerical device physics simulations are used to predict changes inΦ Bbased on these changes in N F and alumina thickness. Surprisingly, Mott–Schottky derivedΦ Bvalues did not follow the trends predicted by these electrostatic models. In fact, there seems to be no discernable effect of N F in diodes with alumina thicknesses below 2 nm, contrary to contactless measurements of the fixed charge of films of similar thickness. TheΦ Btrends are better explained by a dipole model. It is further shown that in as‐deposited MIS diodes, the dipole is a function of alumina layer thickness, whereas in annealed MIS diodes, the dipole andΦ Bwere roughly constant independent of alumina thickness. These data suggest a strategy by which theΦ Bof MIS tunnel contacts can be controlled and which has implication for the design of electrical contacts.