Threshold Voltage Engineering in GaN-Based HFETs: A Systematic Study With the Threshold Voltage Reaching More Than 2 V
M. Martens1, C. Kuhn1, E. Ziffer1, T. Simoneit1, V. Kueller2, A. Knauer2, J. Rass1, T. Wernicke1, S. Einfeldt2, M. Weyers2, and M. Kneissl1,2
Published in:
Appl. Phys. Lett., vol. 108, no. 15, pp. 151108 (2016).
Abstract:
Current injection into AlGaN-based laser diode structures with high aluminum mole fractions for deep ultraviolet emission is investigated. The electrical characteristics of laser diode structures with different p-AlGaN short period superlattice (SPSL) cladding layers with various aluminum mole fractions are compared. The heterostructures contain all elements that are needed for a current-injection laser diode including cladding and waveguide layers as well as an AlGaN quantum well active region emitting near 270 nm. We found that with increasing aluminum content in the p-AlGaN cladding, the diode turn-on voltage increases, while the series resistance slightly decreases. By introducing an SPSL instead of bulk layers, the operating voltage is significantly reduced. A gain guided broad area laser diode structure with transparent p-Al0.70Ga0.30N waveguide layers and a transparent p-cladding with an average aluminum content of 81% was designed for strong confinement of the transverse optical mode and low optical losses. Using an optimized SPSL, this diode could sustain current densities of more than 4.5 kA/cm2.
1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstr. 36, EW 6-1, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
Key Topics:
Aluminium, Laser diodes, Cladding, Heterojunctions, Optical waveguides.
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