High performance single emitter homojunction interfacial work function far infrared detectors

Results are reported on p-GaAs homojunction interfacial work function internal photoemission far infrared (HIWIP FIR) detectors with a ∼1019 cm−3 carbon doped single emitter and a barrier layer for three different barrier thicknesses. A remarkably high quantum efficiency with low dark current and an increased responsivity were observed for devices with 1-, 0.1-, and 4-μm-thick barrier regions. The dark current densities for these structures are on the order of 1–10 μA/cm2 at 4.2 K, corresponding to a high dynamic resistance compared with previous HIWIP FIR detectors. A detector with a barrier thickness of 1 μm had a peak responsivity of 18.6 A/W, a peak detectivity D*=9×1011 cmHz/W, and a quantum efficiency of 40% at a wavelength of 58 μm under a reverse bias measured at 4.2 K. Cutoff wavelengths of these detectors vary with bias and are around 70 μm as expected. The main features of the absorption and responsivity spectra are well described based on a model incorporating free carrier absorption, hot hole transport, and emission over the barrier.