Demonstration of Si homojunction far-infrared detectors

A 48 $\mu \mathrm{m}$ cutoff wavelength ${\mathrm{(\lambda }}_c)$ Si far-infrared (FIR) detector is demonstrated. Internal photoemission over a Si interfacial work-function of a homojunction consisting of molecular beam epitaxy grown multilayers ${\mathrm{(p}}^{+}$ emitter layers and intrinsic layers) is employed. The detector shows high responsivity over a wide wavelength range with a peak responsivity of 12.3$\pm$ 0.1 A/W at 27.5 $\mu \mathrm{m}$ and detectivity $D^{*}$ of 6.6${\text{×10}}^{10}$ $\mathrm{cm}\sqrt{\mathrm{Hz}}\mathrm{/W}$ . The ${\lambda }_c$ and bias dependent quantum efficiency agree well with theory. Based on the experimental results and the model, Si FIR detectors (40–200 $\mu \mathrm{m}$ ) with high performance and tailorable ${\lambda }_c\mathrm{s}$ can be realized using higher emitter layer doping concentrations.