Free-standing AlGaAs thermopiles for improved infrared sensor design

Our group introduced the GaAs/AlGaAs material system for various integrated and micromachined thermoelectric sensors. Investigating the material parameters of Al/sub x/Ga/sub 1-x/As in detail indicates that this material system can be optimized with respect to thermoelectric properties. We demonstrate that figures of merit Z as high as 1.4/spl times/10/sup -4/ K/sup -1/ are predicted. Simultaneously, this material is compatible for micro-machining purposes. The presented infrared sensor is optimized with respect to the material parameter and design. The sensors do not need a supporting membrane and hence undesirable parallel thermal conductance is reduced. Sensors of different geometrical dimensions have been fabricated and compared. Black body measurements result in responsivities up to R=365 V/W and maximum relative detectivities of D/sup */=6.9/spl times/10/sup 8/ cm/spl radic/(Hz)/W which compare to the predicted performance.