Tunneling hot-electron transfer amplifier (THETA) devices, based on GaAs-AlGaAs heterojunctions, were fabricated and tested. Hot-electron transfer (α) through a 1100-Å base in excess of 70% was found at 4.2 K. This resulted in a corresponding current gain (β) in a common emitter configuration of about 2.3. In the temperature range of 4.2-80 K and under constant biasing conditions, α was nearly temperature independent. Electron energy distributions for motion normal to the layers and electron total energy loss while traversing the device were estimated. Typical widths of the energy distributions were less than 200 meV, and both widths and energy peak positions were only slightly dependent on temperature and initial injection energy.