A polymerization process comprising: polymerizing ethylene and optionally one or more α-olefins in the presence of a catalyst to form a semi-crystalline ethylene-based polymer in at least one reactor; the catalyst comprising an organometallic catalyst thereby forming an ethylene-based polymer composition in the at least one reactor, wherein the catalyst is a metal complex of a polyvalent aryloxyether corresponding to the formula: Where M 3 is Ti, Hf or Zr, preferably Zr; Ar 4 is independently in each occurrence a substituted C 9-20 aryl group, wherein the substituents, independently in each occurrence, are selected from the group consisting of alkyl; cycloalkyl; and aryl groups; and halo-, trihydrocarbylsilyl- and halohydrocarbyl-substituted derivatives thereof, with the proviso that at least one substituent lacks co-planarity with the aryl group to which it is attached; T 4 is independently in each occurrence a C 2-20 alkylene, cycloalkylene or cycloalkenylene group, or an inertly substituted derivative thereof; R 21 is independently in each occurrence hydrogen, halo, hydrocarbyl, trihydrocarbylsilyl, trihydrocarbylsilylhydrocarbyl, alkoxy or di(hydrocarbyl)amino group of up to 50 atoms not counting hydrogen; R 3 is independently in each occurrence hydrogen, halo, hydrocarbyl, trihydrocarbylsilyl, trihydrocarbylsilylhydrocarbyl, alkoxy or amino of up to 50 atoms not counting hydrogen, or two R 3 groups on the same arylene ring together or an R 3 and an R 21 group on the same or different arylene ring together form a divalent ligand group attached to the arylene group in two positions or join two different arylene rings together; and R D is independently in each occurrence halo or a hydrocarbyl or trihydrocarbylsilyl group of up to 20 atoms not counting hydrogen, or 2 R D groups together are a hydrocarbylene, hydrocarbadiyl, diene, or poly(hydrocarbyl)silylene group; wherein step is conducted in the presence of from 5 to 20 mmol/m 3 triethylaluminum; and wherein step is conducted in the presence of both of the following conditions: (i) from greater than 0:1 to 65:1 molar ratio of triethylaluminum to the catalyst; and (ii) from 0.1:1 to 5:1 molar ratio of triethylaluminum to modified methylalumoxane. Where M 3 is Ti, Hf or Zr, preferably Zr; Ar 4 is independently in each occurrence a substituted C 9-20 aryl group, wherein the substituents, independently in each occurrence, are selected from the group consisting of alkyl; cycloalkyl; and aryl groups; and halo-, trihydrocarbylsilyl- and halohydrocarbyl-substituted derivatives thereof, with the proviso that at least one substituent lacks co-planarity with the aryl group to which it is attached; T 4 is independently in each occurrence a C 2-20 alkylene, cycloalkylene or cycloalkenylene group, or an inertly substituted derivative thereof; R 21 is independently in each occurrence hydrogen, halo, hydrocarbyl, trihydrocarbylsilyl, trihydrocarbylsilylhydrocarbyl, alkoxy or di(hydrocarbyl)amino group of up to 50 atoms not counting hydrogen; R 3 is independently in each occurrence hydrogen, halo, hydrocarbyl, trihydrocarbylsilyl, trihydrocarbylsilylhydrocarbyl, alkoxy or amino of up to 50 atoms not counting hydrogen, or two R 3 groups on the same arylene ring together or an R 3 and an R 21 group on the same or different arylene ring together form a divalent ligand group attached to the arylene group in two positions or join two different arylene rings together; and R D is independently in each occurrence halo or a hydrocarbyl or trihydrocarbylsilyl group of up to 20 atoms not counting hydrogen, or 2 R D groups together are a hydrocarbylene, hydrocarbadiyl, diene, or poly(hydrocarbyl)silylene group; wherein step is conducted in the presence of from 5 to 20 mmol/m 3 triethylaluminum; and wherein step is conducted in the presence of both of the following conditions: (i) from greater than 0:1 to 65:1 molar ratio of triethylaluminum to the catalyst; and (ii) from 0.1:1 to 5:1 molar ratio of triethylaluminum to modified methylalumoxane. (i) from greater than 0:1 to 65:1 molar ratio of triethylaluminum to the catalyst; and (ii) from 0.1:1 to 5:1 molar ratio of triethylaluminum to modified methylalumoxane.