Mid-Infrared detection in p-GaAs/AlGaAs heterostructures with a current blocking barrier

For the infrared detection in the 3-5 mu m range, p-GaAs/Al(x)Ga1-As-x heterojunction is an attractive material system due to light hole/heavy hole and spin-orbit split-off intra-valance band transitions in this wavelength range. Varying the Al mole fraction (x) provides the tuning for the wavelength threshold, while graded Al(x)Ga1-As-x potential barriers create an asymmetry to allow a photovoltaic operation. The photovoltaic mode of operation offers the advantage of thermal noise limited performance. In our preliminary work, a 2 -6 mu m photovoltaic detector was studied. Implementation of an additional current blocking barrier improved the specific detectivity (D*) by two orders of magnitude, to 1.9x10(11) Jones at 2.7 mu m, at 77K. At zero bias, the resistance-area product (R(0)A) had a value of similar to 7.2x10(8) Omega cm(2), which is five orders higher in magnitude (with a corresponding reduction of the responsivity by only a factor of similar to 1.5), compared to the R(0)A value without the blocking barrier. A photoresponse was observed up to 130K.