Comparison of tunnel junctions for cascaded InAs/GaSb superlattice light emitting diodes
(Color online) Schematic of an electron cascading through two MWIR superlattice emission stages joined with an n-Al0.20In0.80AsSb/p-GaSb tunnel junction. The junction here is biased at 0.7 V (electric field of 0.7 V/0.96 um). Simulation done with one-dimensional diode software.
(Color online) Intrinsic band offsets and bandgaps of materials used on the n-side of the tunnel junction in comparison to GaSb, which is used on the p-side of the junction. Bandgaps and offsets from Ref. 18.
(Color online) Stack diagram of four-stage cascaded LEDs. For the series presented here, the n-side material and/or doping of the tunnel junction was varied.
(Color online) AFM scans of four of the tunnel junctions. In each case, step flow growth of the surface is visible, showing each sample had an atomically smooth surface. Surface roughness and defect density are summarized in Table I for the tunnel junctions: (a) p-GaSb/n-GaSb, (b) p-GaSb/n-symmetrically doped sl grade, (c) p-GaSb/n-GaInAsSb, and (d) p-GaSb/n-AlInAsSb. Not shown are the p-GaSb/n-undoped graded SL and the p-GaSb/n-asymmetrically doped graded SL.
(Color online) (a) 77 K LI curves of 100 × 100 um2 mesa SLED tunnel junction series and (b) associated wallplug efficiencies. Curves shown are the median of 8–10 devices for each sample. Current represents peak of 50 us current pulses at 1% duty cycle.
(Color online) (a) 77 K IV curves and (b) dynamic resistance (dV/dI) of the tunnel junction series corresponding to the LI curves in Fig. 5.
Summary of tunnel junction design, doping, RMS roughness, and defect density of different cascaded LED samples.
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