Full energy peak efficiency quantity

_Geant4 Version:_geant4-v11.2.0
_Operating System:_win11
_Compiler/Version:_Visual Studio Version 17.3.5
_CMake Version:_cmake-3.28.1


Hi everyone, I need help on some matter. In order to calculate my detectors full energy peak efficiency I construct my detector correctly and send gamma rays. But I do not understand what quantity I should track to do this.

When I sending gamma rays in some cases e- secondary is produced due to the compton. This is the only energy deposition event.

What should the energy deposition value be? (Assume I sent 1MeV gamma particle what should be the energy deposition in order to count as “full energy peak”)

Or

Is my approach totally wrong?

Can you help me to understand this please. Thank you.