Mechanically exfoliated gallium oxide (Ga 2 O 3 ) nano sheets based filed-effect-transistors (FETs) with Al 2 O 3 /Ga 2 O 3 , indium gallium zinc oxide (IGZO)/Ga 2 O 3 n-n, and SnO/Ga 2 O 3 p-n heterojunctions in the back-channel were fabricated. In contrast to that Al 2 O 3 /Ga 2 O 3 heterojunction induces negative threshold voltage (<inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula>) shift, both IGZO/Ga 2 O 3 n-n and SnO/Ga 2 O 3 p-n heterojunctions shift <inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula> positively. The Ga 2 O 3 FET with 12 nm p-type SnO realizes enhanced-mode operation with <inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula> of 5.3 V by significantly shifting <inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula> of 40.3 V, high on current density of 14.1mA/mm, and high electron mobility of 191 cm 2 V −1 s −1 , which is, to the best of our knowledge, the highest among the reported Ga 2 O 3 FETs measured at room temperature.