Analysis of characteristics of photodetectors based on InGaAs heteroepitaxial structures for 3D imaging

The 320 × 256 focal plane arrays based on р + -B–n - N + tetralayer heterostructures with a wide-gap barrier layer have been investigated. The heterostructures with a narrow-gap n -InGaAs absorbing layer were grown by means of metalorganic vapor phase epitaxy on InP substrates. The band discontinuity between the In 0.53 Ga 0.47 As absorbing layer and the In 0.52 Al 0.48 As barrier layer is removed by growing a thin four-component n -AlInGaAs layer with the bandgap gradient variation. Delta-doped layers included into the heterostructures make it possible to lower the barrier in the valence band and eliminate the nonmonotonicity of energy levels. The experimental study of the dark current has been performed. It has been revealed that the average value of the dark current does not exceed 10 fA for the photodiode arrays with a pitch of 30 μm.