Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

Abstract

InGaN/GaN micro-light-emitting diodes (micro-LEDs) with a metal–insulator-semiconductor (MIS) structure on the sidewall are proposed to improve efficiency. In this MIS structure, a sidewall electrode is deposited on the insulating layer-coated sidewall of the device mesa between a cathode on the bottom and an anode on the top. Electroluminescence (EL) measurements of fabricated devices with a mesa diameter of 10 µm show that the application of negative biases on the sidewall electrode can increase the device external quantum efficiency (EQE). In contrast, the application of positive biases can decrease the EQE. The band structure analysis reveals that the EQE is impacted because the application of sidewall electric fields manipulates the local surface electron density along the mesa sidewall and thus controls surface Shockley–Read–Hall (SRH) recombination. Two suggested strategies, reducing insulator layer thickness and exploring alternative materials, can be implemented to further improve the EQE of MIS micro-LEDs in future fabrication.

Graphical abstract

Keywords

Micro-LED / GaN / EQE improvement / Micro-fabrication

References

[1] Hwang, D., Mughal, A., Pynn, C.D., Nakamura, S., DenBaars, S.P.: Sustained high external quantum efficiency in ultrasmall blue III–nitride micro-LEDs. Appl. Phys. Express 10(3), 032101 (2017)

[2] Huang, Y., Tan, G., Gou, F., Li, M.C., Lee, S.L., Wu, S.T.: Prospects and challenges of mini-LED and micro-LED displays. J. Soc. Inf. Disp. 27(7), 387–401 (2019)

[3] Konoplev, S.S., Bulashevich, K.A., Karpov, S.Y.: From large-size to micro-LEDs: scaling trends revealed by modeling. Phys. Status Solidi 215(10), 1700508 (2018)

[4] Olivier, F., Daami, A., Licitra, C., Templier, F.: Shockley-read-hall and Auger non-radiative recombination in GaN based LEDs: a size effect study. Appl. Phys. Lett. 111(2), 022104 (2017)

[5] Olivier, F., Tirano, S., Dupré, L., Aventurier, B., Largeron, C., Templier, F.: Influence of size-reduction on the performances of GaN-based micro-LEDs for display application. J. Lumin. 191, 112–116 (2017)

[6] Yin, J., Fathi, E., Siboni, H.Z., Xu, C., Ban, D.: Efficiency degradation induced by surface defects-assisted tunneling recombination in GaN/InGaN micro-light-emitting diodes. Appl. Phys. Lett. 118(2), 021105 (2021)

[7] Boroditsky, M., Gontijo, I., Jackson, M., Vrijen, R., Yablonovitch, E., Krauss, T., Cheng, C.C., Scherer, A., Bhat, R., Krames, M.: Surface recombination measurements on III–V candidate materials for nanostructure light-emitting diodes. J. Appl. Phys. 87(7), 3497–3504 (2000)

[8] Wong, M.S., Hwang, D., Alhassan, A.I., Lee, C., Ley, R., Nakamura, S., DenBaars, S.P.: High efficiency of III-nitride microlight-emitting diodes by sidewall passivation using atomic layer deposition. Opt. Express 26(16), 21324–21331 (2018)

[9] Wong, M.S., Lee, C., Myers, D.J., Hwang, D., Kearns, J.A., Li, T., Speck, J.S., Nakamura, S., DenBaars, S.P.: Size-independent peak efficiency of III-nitride micro-light-emitting-diodes using chemical treatment and sidewall passivation. Appl. Phys. Express 12(9), 097004 (2019)

[10] Zhang, M., Hang, S., Chu, C., Shao, H., Zhang, Y., Zhang, Y., Zhang, Y., Zheng, Q., Li, Q., Zhang, Z.H.: A buried high k insulator for suppressing the surface recombination for GaN-based micro-light-emitting diodes. IEEE Trans. Electron Dev. 69(6), 3213–3216 (2022)

[11] Wang, L., Wang, L., Chen, C.J., Chen, K.C., Hao, Z., Luo, Y., Sun, C., Wu, M.C., Yu, J., Han, Y., Xiong, B., Wang, J., Li, H.: Green InGaN quantum dots breaking through efficiency and bandwidth bottlenecks of micro-LEDs. Laser Photonics Rev. 15(5), 2000406 (2021)

[12] Wang, Z.L., Hao, Z.B., Yu, J.D., Wu, C., Wang, L., Wang, J., Sun, C.Z., Xiong, B., Han, Y.J., Li, H.T., Luo, Y.: Manipulating the band bending of InGaN/GaN quantum dots in nanowires by surface passivation. J. Phys. Chem. C 121(11), 6380–6385 (2017)

[13] Tian, P., McKendry, J.J., Gong, Z., Guilhabert, B., Watson, I.M., Gu, E., Chen, Z., Zhang, G., Dawson, M.D.: Size-dependent efficiency and efficiency droop of blue InGaN micro-light emitting diodes. Appl. Phys. Lett. 101(23), 231110 (2012)

[14] Luke, K.L., Cheng, L.J.: Analysis of the interaction of a laser pulse with a silicon wafer: determination of bulk lifetime and surface recombination velocity. J. Appl. Phys. 61(6), 2282–2293 (1987)

[15] Brody, J., Rohatgi, A.: Analytical approximation of effective surface recombination velocity of dielectric-passivated p-type silicon. Solid-State Electron. 45(9), 1549–1557 (2001)

[16] Schubert, E.F.: Current–voltage characteristics. In: Schubert, E. F. Light-Emitting Diodes (2018), pp. 7–15. E. Fred Schubert (2018)

[17] Piprek, J.: Efficiency droop in nitride-based light-emitting diodes. Phys Status Solidi 207(10), 2217–2225 (2010)

[18] Rigutti, L., Castaldini, A., Cavallini, A.: Anomalous deeplevel transients related to quantum well piezoelectric fields in In_yGa_1−yN/GaN-heterostructure light-emitting diodes. Phys. Rev. B Condens. Matter. Mater. Phys. 77(4), 045312 (2008)

[19] Narita, T., Tokuda, Y., Kogiso, T., Tomita, K., Kachi, T.: The trap states in lightly Mg-doped GaN grown by MOVPE on a freestanding GaN substrate. J. Appl. Phys. 123(16), 161405 (2018)

[20] Chang, L., Yeh, Y.W., Hang, S., Tian, K., Kou, J., Bi, W., Zhang, Y., Zhang, Z.H., Liu, Z., Kuo, H.C.: Alternative strategy to reduce surface recombination for InGaN/GaN micro-light-emitting diodes—thinning the quantum barriers to manage the current spreading. Nanoscale Res. Lett. 15(1), 1–9 (2020)

[21] Jackson, C.M., Arehart, A.R., Cinkilic, E., McSkimming, B., Speck, J.S., Ringel, S.A.: Interface trap characterization of atomic layer deposition Al₂O₃/GaN metal-insulator-semiconductor capacitors using optically and thermally based deep level spectroscopies. J. Appl. Phys. 113(20), 204505 (2013)

[22] Lee, D.H., Lee, J.H., Park, J.S., Seong, T.Y., Amano, H.: Improving the leakage characteristics and efficiency of GaN-based micro-light-emitting diode with optimized passivation. ECS J. Solid State Sci. Technol. 9(5), 055001 (2020)

[23] Lai, S., Lin, W., Chen, J., Lu, T., Liu, S., Lin, Y., Lu, Y., Lin, Y., Chen, Z., Kuo, H.C., Guo, W., Wu, T.: The impacts of sidewall passivation via atomic layer deposition on GaN-based flip-chip blue mini-LEDs. J. Phys. D Appl. Phys. 55(37), 374001 (2022)

[24] Park, S.H., Kim, Y.S., Kim, T.H., Ryu, S.W.: Improved reliability of InGaN-based light-emitting diodes by HfO₂ passivation layer. J. Nanosci. Nanotechnol. 16(2), 1765–1767 (2016)

[25] Patel, M., Jain, B., Velpula, R.T., Nguyen, H.P.T.: Effect of Hfo₂ passivation layer on light extraction efficiency of alinn nanowire ultraviolet light-emitting diodes. ECS Trans. 102(3), 35–42 (2021)

[26] Seong, T.Y., Amano, H.: Surface passivation of light emitting diodes: From nano-size to conventional mesa-etched devices. Surf. Interfaces 21, 100765 (2020)

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