Comparative evaluation of InAs/GaSb superlattices for mid infrared detection: p–i–n versus residual doping

Abstract

We report on the opto-electronic characterization of an InAs/GaSb superlattice (SL) midwave infrared p-i-n photodetector structure (pin-SL) in comparison with the same structure with no intentional doping (i-SL). Both structures were grown on an n-GaSb substrate using molecular beam epitaxy. The nominally undoped structure (i-SL) presented p-i-n like behavior and showed a photovoltaic mode photoresponse due to the residual doping and native defects in this material system. For ∼77 K operation, 0.76 and 0.11 A W -1 responsivity values were obtained at 4 μm from the pin-SL and i-SL structures, respectively. Activation energy analysis showed that the recombination current was dominant in both structures but different recombination centers were involved. The same i-SL structure was also grown on a semi-insulating (SI)-GaAs substrate to study the contribution of the substrate to the carrier density in the SL layers. Temperature dependent Hall effect measurements showed that the nominally undoped structure presented both n-type and p-type conductivities; however, the temperature at which the carrier type switched polarity was observed to be at higher values when the i-SL structure was grown on the SI-GaAs substrate. In addition, a higher carrier density was observed for i-SL on the GaSb substrate than on the GaAs substrate.

Performance evaluation of InAs/GaSb superlattice photodetector grown on GaAs substrate using AlSb interfacial misfit array

“…Especially when the bias was applied on SL-GaAs sample, the optical signal showed considerable improvement (∼5 fold at 3.7 μm) over its photovoltaic mode operation at 300 K (not shown here). Note that the temperature-dependent Hall effect measurements carried out for intrinsic SL structures (designed for MWIR region) indicated that the type of majority carriers and their concentrations are affected by the choice of the substrate: SL samples grown on GaAs exhibits p-type behavior at much wider temperature range in comparison to the SL grown on GaSb [24][25][26]. Therefore, the operating temperature plays an important role for determining the type of minority carriers that conduct the photocurrent, and thus the difference between the optical behaviors under bias might be caused by the different type and density of minority carriers in the corresponding sample.…”