Polarized electron emission from a series of new strained short-period AlInGaAs/AlGaAs superlattices (SLs) is investigated. The In layer content was chosen to give minimal conduction band offset with large strain splitting of the V-band. Simultaneous changing of Al content in both SL layers provides variation of the structure band gap. We demonstrate that tuning of the SL to the excitation energy can be achieved without loss of the electron polarization. The polarization of up to 84% was measured at room temperature.