InGaAs p-i-n detectors with different cap layers

The In0.53Ga0.47As p-i-n detectors with different cap layer which are InP, In0.52Al0.48As without secondly doping, In0.52Al0.48As with epitaxial growth of In0.53Ga0.47As layer and In0.52Al0.48As with secondly doping, respectively, were fabricated. The photoelectric performances of the detectors have been investigated. The result indicated that In0.52Al0.48As cap layer lead to a reduction of dark current compared to InP, but the bad contact property on In0.52Al0.48As can lead to a reduction of quantum efficiency. To get a low resistance contact on p-In0.52Al0.48As, the two methods have been used which are epitaxial growth of In0.53Ga0.47As layer and forming a heavily doped layer on p-InAlAs layer with secondly doping. Although the two methods mentioned above were all beneficial for the contacts properties, epitaxial growth of In0.53Ga0.47As layer can cause deterioration of the property of the detector. The result indicates that the In0.52Al0.48As with secondly doping used as cap layer can lead to lower dark current (dark current density is 116nA/cm(2) at -0.01V) and larger quantum efficiency. The mechanism of dark current and the response spectrum for different samples have also been investigated, for the sample with the In0.52Al0.48As cap layer with secondly doping diffusion current is the main current mechanism.