A Mechanistic Study of GaN Laser Lift-Off

Bret, T.; Wagner, Volker; Dennis, Martin; Hoffmann, P.; Ilegems, M.

doi:10.1002/1521-396x(200212)194:2<559::aid-pssa559>3.0.co;2-s

Cited by 8 publications

(5 citation statements)

References 14 publications

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“…1(a) with a common value 𝑑 s = 0.5 mm. [14,18] As shown in the figure, a linear increase of the interface temperature 𝑇 int is obtained with the increase of the laser energy density 𝐼 0 . In addition, for a narrow pulse width, the increment of 𝑇 int is faster than that for a wide pulse width.…”

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confidence: 71%

“…Because the fluctuation of the pulsed laser energy is inevitable in experiments, [8,15,18] it is important to take the fluctuation into account when calculating the temperature distribution of the GaN film. In ideal cases, for a double polished sapphire substrate, light scattering can be neglected.…”

mentioning

confidence: 99%

“…[15] The fluctuation may come from both the non-uniform energy distribution within the irradiation area and the pulse to pulse variation. [15,18] The GaN film can be fully debonded only when the temperature of the whole irradiated area can reach the decomposition temperature 𝑇 d . Assuming the fluctuation of the pulsed laser energy is 𝑥, then the optimized laser energy density in experiments is 𝐼 ′ = 𝐼 th (1 + 𝑥).…”

mentioning

confidence: 99%

“…Figure 2 shows a comparison of the temperature profiles for pulse widths of 5 ns and 38 ns with 𝑥 = 5%. [15,18] The isotherm contours depict the spatiotemporal history of the temperature. A nonnegligible temperature rise of the sapphire substrate during the laser irradiation is found from the calculation, which has been neglected in previous work.…”

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confidence: 99%

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Effect of Laser Pulse Width on the Laser Lift-off Process of GaN Films

Chi

Zhang

Ying

et al. 2013

Chinese Phys. Lett.

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Laser lift-off (LLO), by which GaN is separated from sapphire, is demonstrated to be a promising technique for advanced GaN-based optoelectronic devices. Its physical insight, however, is still not fully understood. We study systematically the effect of laser pulse width on the LLO process and the property of GaN. To estimate accurately the temperature distribution and the decomposed thickness of GaN, fluctuation in the pulse laser energy is taken into account. It is found that the temperature at the interface is increased in a higher speed for a narrower pulse width. In addition, less damage to the GaN film is expected for a narrower pulse width owing to the smaller heated area, lower transient temperature and lower N2 vapor pressure encountered during LLO. Some experimental results reported in literature are explained well. Our results are useful in understanding the effect of laser pulse width and can be taken as references in LLO of GaN/sapphire structures.

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confidence: 71%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Effect of Laser Pulse Width on the Laser Lift-off Process of GaN Films

Chi

Zhang

Ying

et al. 2013

Chinese Phys. Lett.

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“…The poor heat dissipation of conventional GaN/sapphire LED due to the low thermal conductivity of sapphire substrate leading to high LED junction temperature and degrades the LED performance. Flip-chip [2] and laser lift-off [3] techniques, which use high thermal conductivity substrates, were employed for replacing sapphire to decrease the thermal resistance. For high extraction efficiency, lots of the previous works such as p-GaN surface roughness [4], transparency electrode [5], patterned sapphire substrate [6] and photonic crystals [7] were used to improve the LED performance.…”

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confidence: 99%

Thermal and Optical Improvement of Light-Emitting Diodes with Mesh Pattern on Sapphire Back Delineated by Laser Etching

Lee,

Gong

2008

Meet. Abstr.

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Cathodoluminescence study of InGaN MQW laser diodes using laser lift‐off technique

Kang

et al. 2007

Phys. Status Solidi (c)

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In this paper, spatially integrated or spatially resolved cathodoluminescence (CL) spectroscopy were employed to evaluate the structural and optical changes of InGaN multiple quantum well (MQW) structure before and after Laser lift-off (LLO) process. As for a partially strain-relaxed In 0.1 Ga 0.9 N MQW laser diode (LD) structure with cracking in underlying epitaxial layers, LLO did not cause the blue shift in CL spectra as expected, but rather the red shift induced by the indium diffusion from its abundant regions around cracks. This result could be proved by the monochromated scanning CL images taken at 390 nm and 408 nm not having the same obvious complementary as those of original ones. Compared with calculated laser fluence for LLO, this phenomenon could be mainly attributed to the easy penetration of laser energy via cracks and consequent irradiation absorption within MQWs.1 Introduction Due to difficulties in the growth of bulk GaN, most of III-nitride optoelectronics devices are grown heteroepitaxially on dissimilar sapphire substrates. For III-nitride laser diodes (LDs), a major impediment still remains the efficient dissipation of heat generated from the active area of the device. The high thermal resistance of the sapphire substrate and the relatively high current densities combine to degrade the device performance and lifetimes due to the excessive heating during operation. Therefore, devices fabricated on an electrically and thermally conducting substrate by separating sapphire substrate, are most desirable. Recently, the Laser lift-off (LLO) technique has been used to fabricate the freestanding InGaN LEDs [1, 2] and LDs [3] as well as the creation of GaN substrate.Because of the particular way to accomplish LLO via absorption of laser irradiation within the interface between substrate and epitaxial films, the impacts of LLO on luminescence properties of InGaN MQWs would be complicated by the massive strain-induced cracks commonly seen in the LD structure. In order to evaluate the structural and optical qualities of LD structure before and after LLO, CL in the scanning electron microscope (SEM) had been utilized to study plan-view samples. According to the CL spectra taken at different acceleration voltages (15 kV, 20 kV, 25 kV) before LLO, it was found that indium concentration around cracks which were caused by strain relaxation of underlying layers during growth, was much higher than other regions. After LLO, CL images of the MQWs taken at 390 nm and 408 nm did not have the same obvious complementary as before. Since the spatial homogeneity of CL imaging correlates to the In phase separation in high indium-containing MQWs grown by MOCVD [4], these results indicated that diffusion of indium in solid phase had taken place, considering laser irradiation could readily penetrate the n-type sections beneath MQWs through cracks and be absorbed by them.

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A Mechanistic Study of GaN Laser Lift-Off

Cited by 8 publications

References 14 publications

Effect of Laser Pulse Width on the Laser Lift-off Process of GaN Films

Effect of Laser Pulse Width on the Laser Lift-off Process of GaN Films

Thermal and Optical Improvement of Light-Emitting Diodes with Mesh Pattern on Sapphire Back Delineated by Laser Etching

Cathodoluminescence study of InGaN MQW laser diodes using laser lift‐off technique

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