Ge doped GaN and Al0.5Ga0.5N-based tunnel junctions on top of visible and UV light emitting diodes

Abstract

The use of tunnel junctions (TJs) is a potential solution in blue light-emitting diodes (LEDs) to poor p-contacts, replacing it with another n-contact. TJs are even more advantageous for UV-emitting structures, which suffer from considerably low injection efficiency in high Al concentration UV LEDs. In this article, we report our work on Ge n-doped GaN and AlGaN TJs grown on top of blue and UV LEDs, respectively, by a hybrid growth method. We have achieved state-of-the-art mobility (67 cm2/V s) and resistivity (1.7 × 10-4 ω cm) at a free electron concentration of 5.5 × 1020 cm-3 in Ge-doped GaN. With an emission wavelength of 436 nm, the GaN TJ slightly increased the optical power of the blue LED. The AlGaN TJs, on the other hand, improved the optical power of the UV LED (304 nm) by at least a factor of 3, suggesting the enhancement of the hole injection efficiency by the use of TJs in UV-emitting structures.