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HL: Fachverband Halbleiterphysik

HL 33: Poster II

HL 33.44: Poster

Wednesday, March 29, 2023, 17:00–19:00, P1

The impact of laser lift-off on the optical properties of InGaN/GaN LEDs — •Stefan Wolter, Steffen Bornemann, Hendrik Spende, and Andreas Waag — Institut für Halbleitertechnik, Technische Universität Braunschweig, 38106 Braunschweig

InGaN/GaN LEDs are typically grown on sapphire, but sapphire is a disadvantageous material when it comes to electrical or thermal conductivity. This limits the performance, when the LED structure is processed into a device. For this reason, it is useful to transfer the LED structure to another carrier after growth, which can be achieved by laser lift-off (LLO). In this process, a pulsed laser beam is focused on the sapphire/GaN interface, leading to absorption of the laser photons in the GaN layer and subsequent decomposition of GaN near the interface resulting in detachment of the GaN film from sapphire. The usage of ultra short laser pulses can reduce the required laser fluence compared to nanosecond pulses, but has the disadvantage of penetrating deep into the LED structure and possibly even reaching the active region. This leads to a change in the characteristic properties of the LED, which is investigated in this study. For this purpose, in-house grown blue InGaN/GaN LEDs are investigated before and after LLO, which was conducted with sub-bandgap (520 nm) and above-bandgap (347 nm) laser light at a pulse width of 0.4 ps. Temperature-dependent photoluminescence experiments in the temperature range of 6 K to 295 K indicate that the maximum internal quantum efficiency decreases by at least 10 % after LLO. Furthermore, LLO can have an impact on the localization strength of the carriers inside the active region.