Title: Inhomogeneity of InGaN/GaN MQWs in InGaN based blue LED by atom probe tomography and secondary ion mass spectrometry

Authors: M.A. Ahmad; N.A. Hamzah; R.I.M. Asri; N. Zainal; S.S. Ng; Z. Hassan

Addresses: Institute of Nano Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800, Penang, Malaysia ' Institute of Nano Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800, Penang, Malaysia ' Institute of Nano Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800, Penang, Malaysia ' Institute of Nano Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800, Penang, Malaysia ' Institute of Nano Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800, Penang, Malaysia ' Institute of Nano Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800, Penang, Malaysia

Abstract: In this work, the effect of temperature difference between multi quantum wells (MQWs) and electron blocking layer (EBL) on indium (In) distribution were studied. Each quantum well (QW) and barrier in the active region consisted of an In_0.16Ga_0.84N QW and a GaN barrier grown at a relatively low temperature, while EBL grown at a higher temperature with temperature difference of 220°C. Therefore, the behaviour of indium homogeneity through secondary ion mass spectrometry (SIMS) and atomic probe tomography (APT) was subsequently measured. From the APT measurement, the presence of indium clustering was clearly observed and the MQWs exhibited abrupt interfaces, complementing the result of SIMS measurement, whereby the evidence of indium fluctuation throughout the MQWs was observed. In particular, the indium composition was decreasing in the quantum wells towards the p-sides of the LED. Further, we investigated the effect of indium inhomogeneity towards LEDs performance for in-house growth LED vs. commercial growth LED. Based on the outcome of electroluminescence measurement, it can be concluded that the commercial LED gave better LED performance with less efficiency droop. In future, further optimisations are needed to enhance the In uniformity in the InGaN/GaN MQWs and subsequently improve the LED performance.

Keywords: indium fluctuation; indium clustering; epitaxy; metal organic chemical vapour deposition; SIMS; APT; HRXRD; LED performance.

DOI: 10.1504/IJNT.2022.124509

International Journal of Nanotechnology, 2022 Vol.19 No.2/3/4/5, pp.293 - 303

Published online: 27 Jul 2022 *

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