Patent ID: 7671341

Claim:
An electromagnetic radiation detector responsive to n discrete wavelength ranges, where n is odd and greater than or equal to 3, characterised as λ 0 -λ 1 , λ 1 -λ 2 , . . . , λ n−1 -λ n within a total wavelength range λ 0 -λ n where λ 0 <λ 1 <λ 2 < . . . λ n−1 <λ n , the detector comprising a plurality of layers of semiconductor material providing: a substrate substantially transparent to electromagnetic radiation within said wavelength range λ 0 -λ n ; a first sequence of layers, each doped to provide a first type of electrical conductivity, and each having a different bandgap selected for absorbing radiation up to selected first wavelengths of λ (y+1) , where y=0 or is an even number between 0 and n, in accordance with the value of y; a second sequence of layers, interspersed with layers of said first sequence, each doped to provide a second type of electrical conductivity, and each having a different bandgap selected for absorbing radiation up to selected second wavelengths of λ (z+1) , where z is an odd number from 1 to n−1, in accordance with the value of z, layers of the first sequence alternating with layers of the second sequence; a third sequence of layers, each doped to provide the second type of electrical conductivity, interspersed between said first and second sequence of layers, each of said third sequence of layers, having a bandgap substantially greater than its adjacent layer of said second sequence of layers; and terminals electrically coupled to each layer in said first sequence of layers to apply a bias to said first and second sequence of layers to permit detection of radiation in selected ones of the wavelength ranges λ 0 -λ 1 to λ n−1 -λ n , the number of terminals being determined by (n+1)/2.