Impact of band structure of Ohmic contact layers on the response feature of p-i-n very long wavelength type II InAs/GaSb superlattice photodetector

We show that the energy band structure of the Ohmic contact layers can have a big impact on the response feature of very long wavelength (VLW) detection using p-i-n type II superlattices (SLs). It is found that, if the p and n Ohmic contact layers are comprised of mid wavelength (MW) InAs/GaSb SLs, the photoresponse of the detector is dominated by a short wavelength band with the 50% cutoff wavelength at 2.67 mu m, while the designed VLW response is very weak at 0V. With increasing the bias voltage, the designed VLW response with the 50% cutoff wavelength at 17.8 mu m becomes stronger and stronger. In contrast, if the p and n Ohmic contact layers are made up of the same SLs, as those of the VLW absorber region, only a broad VLW response shows up. The response difference between the two samples is attributed to blocking of the photogenerated carriers by the energy barriers at the interfaces between the absorber and the contact layers for the sample using MW SLs as the contact layers. (C) 2015 AIP Publishing LLC