Studies on abrupt and gradual band gap hole barriers in InAs/GaSb superlattice long wavelength photodetectors

The barrier enhanced InAs/GaSb long wavelength photodetectors were proved to have better performance. Our previous work showed a PBIN detector with an electron barrier inserted show significantly improved electrical performances compared to a PIN structure. To improve the quantum efficiency, Be-doping was employed to convert the conductivity of the long wavelength SL structure, the PN junction moves away from the B-I hetrostructure to the p-N interface which loses the barrier effect. Therefore, the hole barrier was needed to form a PBpBN structure. In this paper, both the abrupt and gradual hole barrier was designed without Al element to form a PBpBN structure. The gradual hole barrier was optimized to avoid the blocking of photo generated current, maximized the quantum efficiency. The R(max)A product of the PBpBN detector was measured to be 77 Omega cm(2) and the dark current density under -0.05V bias was measured to be 8.8x10(-4)A/cm(2) at 80K. The quantum efficiency of gradual hole barrier detector was measured to be 27.2% at 10.6 mu m and the quantum efficiency was slowly decreased under reverse bias. The result shows the gradual hole barrier efficiently eliminate the peak barrier in the electron band. The peak detectivity of this graded detector is calculated to be 9.46x10(10)cm.Hz(1/2).W-1 at 10.6 mu m.