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GaN-on-Si blue/white LEDs: epitaxy, chip, and package

Qian Sun1, 2, 3, , Wei Yan1, 4, Meixin Feng1, Zengcheng Li2, 3, Bo Feng2, 3, Hanmin Zhao2, 3 and Hui Yang1

+ Author Affiliations

 Corresponding author: Qian Sun, Email:qsun2011@sinano.ac.cn

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Abstract: The dream of epitaxially integrating Ⅲ-nitride semiconductors on large diameter silicon is being fulfilled through the joint R&D efforts of academia and industry, which is driven by the great potential of GaN-on-silicon technology in improving the efficiency yet at a much reduced manufacturing cost for solid state lighting and power electronics. It is very challenging to grow high quality GaN on Si substrates because of the huge mismatch in the coefficient of thermal expansion (CTE) and the large mismatch in lattice constant between GaN and silicon, often causing a micro-crack network and a high density of threading dislocations (TDs) in the GaN film. Al-composition graded AlGaN/AlN buffer layers have been utilized to not only build up a compressive strain during the high temperature growth for compensating the tensile stress generated during the cool down, but also filter out the TDs to achieve crack-free high-quality n-GaN film on Si substrates, with an X-ray rocking curve linewidth below 300 arcsec for both (0002) and (1012) diffractions. Upon the GaN-on-Si templates, prior to the deposition of p-AlGaN and p-GaN layers, high quality InGaN/GaN multiple quantum wells (MQWs) are overgrown with well-engineered V-defects intentionally incorporated to shield the TDs as non-radiative recombination centers and to enhance the hole injection into the MQWs through the via-like structures. The as-grown GaN-on-Si LED wafers are processed into vertical structure thin film LED chips with a reflective p-electrode and the N-face surface roughened after the removal of the epitaxial Si(111) substrates, to enhance the light extraction efficiency. We have commercialized GaN-on-Si LEDs with an average efficacy of 150-160 lm/W for 1 mm2 LED chips at an injection current of 350 mA, which have passed the 10000-h LM80 reliability test. The as-produced GaN-on-Si LEDs featured with a single-side uniform emission and a nearly Lambertian distribution can adopt the wafer-level phosphor coating procedure, and are suitable for directional lighting, camera flash, streetlighting, automotive headlamps, and otherlighting applications.

Key words: Ⅲ-nitride semiconductorsLEDGaN-on-Si



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Fig. 1.  (Color online) Schematic diagram of the stress evolution during growth and cool-down for GaN film grown on (a) sapphire,and silicon substrates (b) without and (c) with Al-composition graded AlGaN/AlN buffer layers.

Fig. 2.  (Color online) Cross-sectional TEM view of GaN-on-Si LED epitaxial film. (a) Al-composition graded AlGaN/AlN/Si interface region. (b) InGaN/GaN MQWs region.

Fig. 3.  (Color online) Double crystal X-ray rocking curves (DCXRCs) of (0002) and (10$\bar1$2) diffractions for 3.6-$\mu $m-thick n-GaN([Si] doping 8 × 10$^{18}$ cm$^{-3}$) grown on Si(111) substrates.

Fig. 4.  (Color online) GaN-on-Si LED epitaxy production data. (a) Average PL wavelength. (b) Average wavelength STD. (c) 2-inch wafer bow. (d) 6-inch wafer bow.

Fig. 5.  (Color online) Schematic of the vertical structure thin film (TF) chip process of GaN-on-Si LEDs.

Fig. 6.  SEM images of a series of TF chip product of GaN-on-Si LEDs.

Fig. 7.  (Color online) GaN-on-Si LED 1 mm$^{2}$ high power chip wafer-level test mapping of (a) light output (LOP) and (b) voltage of bare chips at 350 mA,(c) leakage current $I_{\rm r}$ at a reverse bias of 5 V,and (d) wavelength.

Fig. 8.  Statistic histogram of the probe test data of a typical batch of GaN-on-Si LED wafers processed into 1 mm$^{2}$ high power blue chips. (a) Light output (LOP) and (b) voltage of bare chips at 350 mA,(c) leakage current $I_{\rm r}$ at a reverse bias of 5 V,and (d) wavelength.

Fig. 9.  (Color online) LM80 reliability test light output decay data of packaged LEDs of 1 mm$^{2}$ GaN-on-Si chips: each data point represents an average of 25 chips test data. The light output decay is very limited after 10000 h accelerated burn-in test at elevated temperature.

Fig. 10.  (Color online) (a) Processed 6-inch GaN-on-Si LED wafer,and (b) its lit-up photo under a forward injection current.

Fig. 11.  (Color online) Angular distribution of light from thin film GaN-on-Si and GaN-on-PSS LED chips.

Fig. 12.  (Color online) GaN-on-Si high power blue LED chips (a) can be converted into direct white chips (b) before chip dicing through a wafer-level phosphor coating process,followed by 3535 ceramic package (c).

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    Received: 01 December 2015 Revised: Online: Published: 01 April 2016

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      Qian Sun, Wei Yan, Meixin Feng, Zengcheng Li, Bo Feng, Hanmin Zhao, Hui Yang. GaN-on-Si blue/white LEDs: epitaxy, chip, and package[J]. Journal of Semiconductors, 2016, 37(4): 044006. doi: 10.1088/1674-4926/37/4/044006 Q Sun, W Yan, M X Feng, Z C Li, B Feng, H M Zhao, H Yang. GaN-on-Si blue/white LEDs: epitaxy, chip, and package[J]. J. Semicond., 2016, 37(4): 044006. doi: 10.1088/1674-4926/37/4/044006.Export: BibTex EndNote
      Citation:
      Qian Sun, Wei Yan, Meixin Feng, Zengcheng Li, Bo Feng, Hanmin Zhao, Hui Yang. GaN-on-Si blue/white LEDs: epitaxy, chip, and package[J]. Journal of Semiconductors, 2016, 37(4): 044006. doi: 10.1088/1674-4926/37/4/044006

      Q Sun, W Yan, M X Feng, Z C Li, B Feng, H M Zhao, H Yang. GaN-on-Si blue/white LEDs: epitaxy, chip, and package[J]. J. Semicond., 2016, 37(4): 044006. doi: 10.1088/1674-4926/37/4/044006.
      Export: BibTex EndNote

      GaN-on-Si blue/white LEDs: epitaxy, chip, and package

      doi: 10.1088/1674-4926/37/4/044006
      Funds:

      Project supported financially by the National Natural Science Foundation of China (Nos. 61522407, 61534007, 61404156), the National High Technology Research and Development Program of China (No. 2015AA03A102), the Science & Technology Program of Jiangsu Province (Nos. BA2015099, BE2012063), the Suzhou Science & Technology Program (No. ZXG2013042), and the Recruitment Program of Global Experts (1000 Youth Talents Plan). Project also supported technically by Nano-X from SINANO, CAS

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      • Corresponding author: Email:qsun2011@sinano.ac.cn
      • Received Date: 2015-12-01
      • Accepted Date: 2015-12-02
      • Published Date: 2016-01-25

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