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

For the infrared detection in the 3-5 μm range, p-GaAs/AlxGa1-xAs 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 AlxGa1-xAs 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 μm photovoltaic detector was studied. Implementation of an additional current blocking barrier improved the specific detectivity (D∗) by two orders of magnitude, to 1.9×1011 Jones at 2.7 μm, at 77K. At zero bias, the resistance-area product (R0A) had a value of ∼ 7.2×108 Ω cm2, which is five orders higher in magnitude (with a corresponding reduction of the responsivity by only a factor of ∼ 1.5), compared to the R0A value without the blocking barrier. A photoresponse was observed up to 130K.