Regensburg 2025 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 33: Nitrides: Devices
HL 33.5: Vortrag
Mittwoch, 19. März 2025, 12:15–12:30, H15
Influence of strain reduced HTA-AlN/sapphire templates with different offcuts on the performance of UVC LEDs — •Sarina Graupeter1, Finn Kusch1, Paula Vierck1, Sylvia Hagedorn2, Markus Weyers2, Tim Wernicke1, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics, Berlin, Germany — 2Ferdinand-Braun-Institut (FBH), Berlin, Germany
High temperature annealing (HTA) of sputter dposited AlN layers on (0001) sapphire substrates allows for fabrication low threading dislocation densitiy templates (TDD of 4 x 108 cm2) enabling UVC LEDs with improved external quantum efficiency and lifetime. However, due to the thermal expansion mismatch of the sapphire and the AlN, the AlN layers are under high compressive strain after cooling down from HTA at 1700∘C. This can lead to strain relaxation and formation of dislocation half-loops during the subsequent growth of AlN and AlGaN layers, thus decreasing the radiative recombination efficiency (RRE). By growing a Si-doped AlN layer on HTA-AlN the in-plane compressive strain єxx is reduced by around 30% from -0.3 to -0.2. The impact of such an interlayer on the electro-optical properties of UVC-LEDs has been investigated with focus on the RRE. The RRE has been determined using cw and pulsed EL-measurements with the Titkov-Dai method. Using an AlN:Si interlayer shows an increase of the EQE value from 0.8% to 1%. Emission powers as high as 1.9 mW at 50 mA can be realized for UVC LEDs on strain reduced templates.