Need component that switches on a higher voltage and current
Your description sounds like:







simulate this circuit &ndash; Schematic created using CircuitLab

In this circuit the transistor is an emitter follower.  The emitter voltage will be 0.7 volts less than the base voltage.

You should instead do:







simulate this circuit

With this circuit the transistor will act as a switch, and will have about 0.2 volts between emitter and collector when the base is pulled up by the ATMega output.