Surface channel current in InAs∕GaSb type-II superlattice photodiodes

Abstract

We observed experimental evidences of surface channel current on the sidewall of InAs∕GaSb superlattice photodiodes. We investigated the surface channel current by measuring the current-voltage (I-V) characteristics of the diodes. The experimental data compare very well with our theoretical model before and after ammonium sulfide passivation. By using the passivation, we reduced the surface channel current by five times, which supports that the surface channel current is induced by surface carriers. We believe that the surface channel current results from the inversion layer of a p-type superlattice with surface Fermi levels pinned above the conduction-band minimum in InAs∕GaSb superlattices.

Low-frequency noise behavior at reverse bias region in InAs/GaSb superlattice photodiodes on mid-wave infrared

“…The GR E act is 0.12 eV (e.g. for SiO 2 -passivated sample), which is half of the band gap as expected in the literature [15]. For different passivation layers, a different deviation from Arrhenius fit was observed for 65 -95 K. In this temperature range, the dominating current mechanism is the surface limited current [10], which is somewhat suppressed in the SiO 2 sample in contrast to other samples at zero bias.…”

“…The value of carrier concentration (n s ) is strongly dependent on the operation bias voltages at constant temperature, and leads to the exponential behavior of E act, which results in the analytical expression n s ~ exp(-E act /k B T) where n s is the charge carrier concentrations [15,16]. By assuming, n s are proportional to the leakage current I lc with a proportionality factor of I c .…”

“…The activation energy of the current limiting factors at different reverse bias values can be determined from the slope of the linear fit to ln(RA) vs. 1000/T for different reverse voltages (see Figure 7) [14,15]. Figure 6 shows the E act vs. reverse V bias for all SL diodes.…”

Surface Recombination Noise in InAs/GaSb Superlattice Photodiodes

“…The GR E act is 0.12 eV (for SiO 2 -passivated sample), which is half of the band gap as expected in the literature. 16) For different passivations, different deviations from the Arrhenius fit were observed for the temperature range of 65-95 K. In this temperature range and at À0:1 V bias, the surface-limited current is 1-2 orders of magnitude suppressed in the SiO 2 -passivated device while Si 3 N 4 passivation increases it by about an order of magnitude in comparison with the unpassivated device. Hence, the deviations seen in Fig.…”

“…4(b)] on n s as n s $ expðÀE act = k B T Þ. 16,18) From this assumption, the leakage current, I lc (A), can be written as I lc ¼ I c expðÀE act =k B T Þ, where I c is a prefactor.…”