Solar‐blind AlGaN MSM photodetectors with 24% external quantum efficiency at 0 V

By utilising an asymmetric metallisation scheme to fabricate an AlGaN‐based solar‐blind metal–semiconductor–metal photodetector, a zero‐bias external quantum efficiency (EQE) of 24% for illumination at 240 nm wavelength from the substrate side was obtained. Moreover, an asymmetric bias‐dependence of dark current and EQE is observed. The EQE saturates at about 38% in reverse direction, whereas in forward direction the presence of an internal gain mechanism is indicated.