GaAs multilayer p+-i homojunction far-infrared detectors

A molecular beam epitaxy grown wavelength tunable GaAs $p^{+}$ -$i$ homojunction interfacial work-function internal photoemission far-infrared detector is developed. The multilayer ${\mathrm{(p}}^{+}$ -$i$ -$p^{+}$ -$i$ -…) detector structures consist of 2, 5, and 10 emitter layers. Experimental results are explained in terms of the number of emitter layers and the doping concentrations of the emitter layer. A detector with 10 multilayers and an emitter layer doping concentration ${\mathrm{(N}}_e)$ of ${\text{3×10}}^{18}$ cm${}^{\text{−3}}$ shows a current responsivity of 2 A/W, an effective quantum efficiency of 9.2% (at 26.3 $\mu$ m) with a cutoff wavelength of 85 $\mu$ and the noise equivalent power of 2.18$\times$ 10${}^{\text{−12}}$ W/$\sqrt{\mathrm{Hz}}$ at 4.2 K.