Regensburg 2019 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 2: Nitrides: Devices
HL 2.4: Talk
Monday, April 1, 2019, 10:15–10:30, H31
Realizing tunnel junctions in semiconductors with bandgap higher than 5 eV for electro-optical applications — •Luca Sulmoni1, Christian Kuhn1, Martin Guttmann1, Johannes Glaab2, Norman Susilo1, Tim Wernicke1, Markus Weyers2, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics — 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin
A highly conductive UV transparent layer is needed to overcome the poor current spreading of p-electrodes in deep UV LEDs. This is mainly caused by the high sheet and contact resistance of the transparent p-AlGaN layers and results in very large operating voltages. A promising alternative to standard p-electrodes is the injection of holes into the heterostructure by means of efficient tunnel junctions (TJs) allowing for low resistivity n-contacts on both sides of the device. This way, a transparent top n-layer can be used as an excellent native current spreading layer and a metal reflector could be used to enhance the light extraction. We have successfully demonstrated AlGaN-based TJ-LEDs emitting at 271 nm grown entirely by MOVPE. A GaN-based thin interlayer was implemented to facilitate carrier tunneling at the TJ interface. Without interlayer, current injection and light emission was possible but at extremely high operation voltages exceeding 40 V and low current levels. Typically, the operation voltages and the output powers of a 0.35 mm2 TJ-LED featuring an GaN interlayer of 8 nm are 24 V and 1.3 mW, respectively, measured at 20 mA on wafer in cw operation. A maximum EQE of 1.4% is reached at 40 mA.