A bispectral detector comprising upper and lower semiconductor layers of a first conductivity type in order to absorb a first and a second electromagnetic spectrum, separated by an intermediate layer that forms a barrier; semiconductor zones of a second conductivity type implanted in upper layer and lower layer and each implanted at least partially in the bottom of an opening that passes through upper layer and intermediate layer; and conductor elements connected to semiconductor zones. At least that part of each opening that passes through upper layer is separated from the latter by a semiconductor cap layer: whereof the concentration of dopants of the second conductivity type is greater than 1017 cm−3; and whereof the thickness is chosen as a function of said concentration so that it exceeds the minority carrier diffusion length in the cap layer.