Long-wavelength infrared InAs/GaSb type-II superlattice PπBN photodetectors are demonstrated on GaSb substrates. The focal plane array device consists of a 2.0μm thick absorber layer and has a 50% cutoff wavelength of 11.3μm, and a maximum resistance-area product of 800 Ω•cm2 at 77 K. And the resistance-area product stay above 500 Ω•cm2 at the range from -200 mV to -1100 mV. These single units show good consistency. It has laid a reliable foundation for the manufacturing of focal plane arrays.
In this article, the band structures of InAs/InAsSb superlattices are calculated by sp3s* model, which is based on empirical tight-bonding method (ETBM). First, the band structures of InAs/InAsSb superlattice with varies period are calculated, the calculated bandgap results are consistent with experiment values. The conduction band edge (Ec level) for the two sets of InAs/InAsSb T2SLs are approximately independent of the cutoff wavelength (or band gap), and they are significantly lower than the conduction band edges of InAs/GaSb. The relationship between periodic structure and cutoff wavelength is obtained under the condition of strain balance. Then the holes effective mass at Γ point of mini-band along the growth direction for different structure InAs/InAsSb superlattice are derived. Finally, the composition segregation function is included in our model in order to study the impact of Sb segregation on InAs/InAsSb superlattice. These material parameters obtained from our calculated results can be used in the design of T2SL-based IR detectors.
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