LI Tian-bao, ZHAO Guang-zhou, LU Tai-ping etc. Effect of Undoped GaN Layer Thickness on The Wavelength Uniformity of GaN Based Blue LEDs[J]. Chinese Journal of Luminescence, 2017,38(9): 1198-1204
LI Tian-bao, ZHAO Guang-zhou, LU Tai-ping etc. Effect of Undoped GaN Layer Thickness on The Wavelength Uniformity of GaN Based Blue LEDs[J]. Chinese Journal of Luminescence, 2017,38(9): 1198-1204 DOI: 10.3788/fgxb20173809.1198.
Effect of Undoped GaN Layer Thickness on The Wavelength Uniformity of GaN Based Blue LEDs
InGaN based blue light emitting diodes(LED) with different thickness of undoped GaN (u-GaN) layer were grown on
c
-plane pattern sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The structure and photoelectric properties were characterized by
in-situ
wafer bowing measurements
high-resolution X-ray diffraction(HRXRD) and photoluminescence (PL). Due to the different thermal expansion coefficients between the sapphire and the epitaxial film
the curvature of wafer varies constantly in the progress of temperature changing. It is found that the wafer presents concave bowing at the end of n-GaN growth directly affects the wafer status of bowing during the MQWs growth. The wafer with 3.63 m u-GaN layer is under the biggest bowing status indicating that the stress value of n-GaN is the maximum. In the subsequent lower temperature MQWs deposition stage
the concave deformation constantly decreases
and even transforms into the convex deformation. The
in-situ
wafer bowing measurements results are in accordance with the PL-mapping tests. The wafer with better uniformity and consistency can be obtained by adjusting the thickness of u-GaN layer which can change the status of stress in the epitaxial structures
and finally be beneficial to reduce the processing time and the cost of the LED chips.
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references
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