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HL: Fachverband Halbleiterphysik

HL 2: Nitrides: Devices

HL 2.5: Vortrag

Montag, 1. April 2019, 10:30–10:45, H31

Small-area current injection in GaN-based light emitters with tunnel junctions — •Christoph Berger, Silvio Neugebauer, Cleophace Seneza, Jürgen Bläsing, Armin Dadgar, and André Strittmatter — Otto-von-Guericke-Universität Magdeburg, Deutschland

MOVPE-grown GaN:Mg/GaN:Ge tunnel junctions enable surface emitting devices such as LEDs and laser diodes with low absorption losses. Efficient activation of hydrogen passivated Mg acceptors requires a combination of in-situ activation directly after the GaN:Mg growth step and ex-situ thermal annealing at 800^∘C after mesa etching to enable hydrogen out-diffusion from the sidewalls. Excellent lateral current spreading in large area LEDs is confirmed by a homogeneous electroluminescence distribution across the whole mesa area. By optimization of the doping profile, tunnel junction LEDs with negligible increase in bias voltage compared to conventional LEDs with Ni/Au contacts were realized. Light output at 430 nm wavelength through the p-contact region is enhanced by -0.9ex~70% due to better transparency of the GaN:Ge with regard to the semitransparent Ni/Au contact. Application of these GaN:Mg/GaN:Ge tunnel-junctions in small-area light emitters like µ-LEDs (diameter < 50 µm) or vertical-cavity surface-emitting lasers. A first remarkable result is pulsed operation of such devices at current-densities up to 10 kA/cm². We will further report on lateral current confinement to realize injection areas below 10 µm.