Improvement of the transfer coefficient of GaAs/Si spin-valve transistors

Nowadays GaAs/Si hot electron spin-valve transistors can be readily made using the vacuum bonding technique. They show sharp variations in collector current in small magnetic fields, good for sensor applications. However, the transfer coefficient of the device, defined as collected current over injected current, is only around 10−4%. We address the structural properties of GaAs/Si spin-valve transistors that influence the transfer coefficient. An improvement of the transfer coefficient of more than one order of magnitude is obtained by implementing a GaAs/AlAs emitter launcher maintaining 93% of relative collector current change.