  We have investigated the spin-dependent transport properties of GaMnAs-based
three-terminal semiconductor spin hot-carrier transistor (SSHCT) structures.
The emitter-base bias voltage VEB dependence of the collector current IC,
emitter current IE, and base current IB shows that the current transfer ratio
alpha (= IC / IE) and the current gain beta (= IC / IB) are 0.8-0.95 and 1-10,
respectively, which means that GaMnAs-based SSHCTs have current amplifiability.
In addition, we observed an oscillatory behavior of the tunneling
magnetoresistance (TMR) ratio with the increasing bias, which can be explained
by the resonant tunneling effect in the GaMnAs quantum well.
