  The expected increase of total integrated luminosity by a factor ten at the
HL-LHC compared to the design goals for LHC essentially eliminates the safety
factor for radiation hardness realized at the current cold amplifiers of the
ATLAS Hadronic End-cap Calorimeter (HEC). New more radiation hard technologies
have been studied: SiGe bipolar, Si CMOS FET and GaAs FET transistors have been
irradiated with neutrons up to an integrated fluence of 2.2 x 10^{16} n/cm^2
and with 200 MeV protons up to an integrated fluence of 2.6 x 10^{14} p/cm^2.
Comparisons of transistor parameters such as the gain for both types of
irradiations are presented.
