A femtosecond laser focused inside bulk GaN was used to slice a thin GaN film with an epitaxial device structure from a bulk GaN substrate. The demonstrated laser slicing lift-off process did not require any special release layers in the epitaxial structure. GaN film with a thickness of 5 µm and an InGaN LED epitaxial device structure was lifted off a GaN substrate and transferred onto a copper substrate. The electroluminescence of the LED chip after the laser slicing lift-off was demonstrated.
Представлены результаты исследования зависимостей тока и емкости от прямого смещения диодов Шоттки Au/n-GaN, а также спектров подзонного оптического поглощения и дефектной фотолюминесценции объемных кристаллов и тонких слоев n-GaN. Показано, что туннелирование с участием дефектов является доминирующим механизмом транспорта при прямых смещениях контактов Шоттки на n-GaN. Зависимости тока и емкости от прямого смещения отражают энергетический спектр дефектов в запрещенной зоне n-GaN: рост с энергией плотности глубоких состояний, ответственных за желтую фотолюминесценцию в GaN, и резкий экспоненциальный хвост состояний с урбаховской энергией EU=50 мэВ вблизи края зоны проводимости. Уменьшение частоты перескоков электронов вблизи интерфейса Au/n-GaN приводит к широкому распределению локальных времен диэлектрической релаксации и изменению распределения электрического поля в области пространственного заряда при прямых смещениях. DOI: 10.21883/FTP.2017.09.44888.8528
Cracking of thick GaN films on sapphire substrates during the cooling down after the growth was studied. The cracking was suppressed by increasing the film-to-substrate thickness ratio and by using an intermediate carbon buffer layer, that reduced the binding energy between the GaN film and the substrate. Wafer-scale self-separation of thick GaN films has been demonstrated.
A free-standing bulk gallium nitride layer with a thickness of 365 µm and a diameter of 50 mm was obtained by hydride vapor phase epitaxy on a sapphire substrate with a carbon buffer layer. The carbon buffer layer was deposited by thermal decomposition of methane in situ in the same process with the growth of a bulk GaN layer. The bulk GaN layer grown on the carbon buffer layer self-separated from the sapphire substrate during the cooling after the growth. The dislocation density was 8 · 10 6 cm −2 . The (0002) X-Ray rocking curve full width at half maximum was 164 arcsec. arXiv:1902.04672v2 [physics.app-ph] 17 Apr 2019 V. Voronenkov et al 2019
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