Evolution of femtosecond laser-induced damage in doped GaN thin films

Femtosecond Laser Lift‐Off with Sub‐Bandgap Excitation for Production of Free‐Standing GaN Light‐Emitting Diode Chips

“…As expected, ϕ th stays rather constant over the working distance, slightly deviating between 0.4 and 0.55 J cm −2 , with a mean of 0.5 J cm −2 . In the literature, values between 0.25 and 0.9 J cm −2 were reported for single femtosecond pulse impingement on GaN . Ščiuka et al and Grinys et al tested the damage threshold in quite a similar regime to the one demonstrated in this work, utilizing 515 nm pulses of 325 fs width, where they measured a threshold of 0.4 J cm −2 for single pulses .…”

“…Even when taking Fresnel reflection at the GaN/air interface into consideration for the threshold fluence, the previously determined value of ϕ th is lowered by 17% and still reaches 0.4 J cm −2 . As consistently reported in the literature, there is an incubation effect, meaning that the laser‐induced damage threshold is lowered if a spot on a sample is hit several times by impinging pulses . This mechanism is explained by ongoing crystal modifications during repetitive laser treatment.…”

“…In the literature, values between 0.25 and 0.9 J cm −2 were reported for single femtosecond pulse impingement on GaN . Ščiuka et al and Grinys et al tested the damage threshold in quite a similar regime to the one demonstrated in this work, utilizing 515 nm pulses of 325 fs width, where they measured a threshold of 0.4 J cm −2 for single pulses . That value is in good agreement with the one measured in our study.…”

“…As consistently reported in the literature, there is an incubation effect, meaning that the laserinduced damage threshold is lowered if a spot on a sample is hit several times by impinging pulses. [35,38,42] This mechanism is explained by ongoing crystal modifications during repetitive laser treatment. While scanning over the surface as sketched in Figure 4b, every part of the sample was located within the beam area several times.…”

One-Step Fabrication Method of GaN Films for Internal Quantum Efficiency Enhancement and Their Ultrafast Mechanism Investigation

“…Also, previous studies mainly focused on the analysis of the morphology and elemental characterization of GaN after femtosecond laser processing. 19,20 As we know, in the fabrication process using femtosecond lasers, the laser− material interaction is a nonlinear and nonequilibrium ultrafast process. 21 The photon−electron interaction between the femtosecond laser and material directly determines the morphologies and properties of the final structures, thus affecting the performance of the device.…”