Broad-band photoresponse from InAs quantum dots embedded into InGaAs graded well

A broad-band photoresponse is obtained from undoped InAs multiple quantum dots grown by the molecular beam epitaxy (MBE) technique on a (100) GaAs substrate. The quantum dots were embedded in an In/sub x/Ga/sub 1-x/As graded well where the In mole fraction is chosen in the range of 0.3 /spl ges/ x /spl ges/ 0.0. The photoresponse of the reversed biased device, obtained at 80.5 K and using the normal incident configuration, was found to span the spectral range of 3.5 - 9.5 μm. While the photoresponse is significantly high under the influence of the reverse bias voltage, the forward bias photoresponse is found to be negligible.