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Title: Stress-induced piezoelectric field in GaN-based 450-nm light-emitting diodes

We investigated the influence of the built-in piezoelectric field induced by compressive stress on the characteristics of GaN-based 450-nm light-emitting diodes (LEDs) prepared on sapphire substrates of different thicknesses. As the sapphire substrate thickness was reduced, the compressive stress in the GaN layer was released, resulting in wafer bowing. The wafer bowing-induced mechanical stress altered the piezoelectric field, which in turn reduced the quantum confined Stark effect in the InGaN/GaN active region of the LED. The flat-band voltage was estimated by measuring the applied bias voltage that induced a 180° phase shift in the electro-reflectance (ER) spectrum. The piezoelectric field estimated by the ER spectra changed by ∼110 kV/cm. The electroluminescence spectral peak wavelength was blue-shifted, and the internal quantum efficiency was improved by about 22% at a high injection current of 100 mA. The LED on the 60-μm-thick sapphire substrate exhibited the highest light output power of ∼59 mW at an injection current of 100 mA, with the operating voltage unchanged.
Authors:
 [1] ;  [2] ; ;  [1]
  1. Department of Materials Science and Engineering, Chonnam National University, Yongbong 300 Gwangju 500-757 (Korea, Republic of)
  2. (Egypt)
Publication Date:
OSTI Identifier:
22308193
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 16; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CURRENTS; ELECTRIC POTENTIAL; ELECTROLUMINESCENCE; GALLIUM NITRIDES; INJECTION; LAYERS; LIGHT EMITTING DIODES; PHASE SHIFT; PIEZOELECTRICITY; QUANTUM EFFICIENCY; REFLECTION; SAPPHIRE; SPECTRA; STARK EFFECT; STRESSES; SUBSTRATES; THICKNESS; VISIBLE RADIATION; WAVELENGTHS