  We report on n-type degenerate doping in MOVPE grown
\b{eta}-(Al0.26Ga0.74)2O3 epitaxial thin films and modulation doping in
\b{eta}-(Al0.26Ga0.74)2O3/\b{eta}-Ga2O3 heterostructure. Alloy composition is
confirmed using HRXRD measurements. Carrier concentration in the thin films is
proportional to the silane molar flow. Room temperature hall measurements
showed a high carrier concentration of 6x1018-7.3x1019 cm-3 with a
corresponding electron mobility of 53-27 cm2/V.s in uniformly-doped
\b{eta}-(Al0.26Ga0.74)2O3 layers. Modulation doping is used to realize a total
electron sheet charge of 2.3x1012 cm-2 in a
\b{eta}-(Al0.26Ga0.74)2O3/\b{eta}-Ga2O3 heterostructure using a uniformly-doped
\b{eta}-(Al0.26Ga0.74)2O3 barrier layer and a thin spacer layer.
