Overview
IEC 60747-5-15:2022 defines a standardized test method to measure the flat‑band voltage (VFB) of single GaN‑based light emitting diode (LED) die or packages (without phosphor) using electroreflectance (ER) spectroscopy. The standard explains the ER measurement setup, environmental and instrument conditions, the measurement sequence to locate the flat‑band voltage, and how VFB can be used to determine the internal electric field in the LED active region. White LEDs for lighting applications are explicitly out of scope.
Key topics and requirements
- Scope & purpose
- Measurement of flat‑band voltage of single GaN‑based LEDs (die or package without phosphor).
- VFB is used to derive the internal electric field across quantum wells.
- Measurement principle
- ER spectroscopy monitors the modulated reflectance signal (ΔR/R) produced by applying a small modulation voltage ΔV on top of a DC bias V.
- The flat‑band voltage is identified where the ER response to the modulation is minimal and a phase inversion of the ER signal occurs as DC bias crosses VFB.
- Test setup
- Function generator for DC + modulation voltage (V + ΔV), monochromator for wavelength selection, photomultiplier tube (PMT) for reflected light detection, and a lock‑in amplifier.
- Spectrally resolved ΔR/R is recorded and the ER peak amplitude is plotted versus bias to find the intercept (VFB).
- Environmental and instrument conditions
- Ambient temperature default: 25 ± 3 °C (natural convection).
- Relative humidity: 25 % RH to 75 % RH.
- Thermal equilibrium requirement when heat affects measurements.
- Instruments referenced are aligned with IEC 60747‑5‑6:2021 measuring equipment requirements.
- Output
- Test report elements and optional calculation of internal electric field using VFB together with known microstructural parameters (layer widths, built‑in voltage).
Applications and who uses it
- Device characterization and R&D: LED researchers and device engineers use the method to quantify internal electric fields and polarization effects in InGaN/GaN quantum wells.
- Quality control & process monitoring: Manufacturers apply the standard for pass/fail criteria and process drift detection on LED wafers or packaged dies (without phosphor).
- Failure analysis & supplier validation: Test labs and integrators rely on ER‑based VFB measurements to verify device consistency and to investigate electrical/optical anomalies.
Related standards
- IEC 60747‑5‑6:2021 (Optoelectronic devices - Light emitting diodes) - referenced for measuring instruments and equipment.
- Other parts of the IEC 60747 series cover broader semiconductor device and optoelectronic testing practices.
Keywords: IEC 60747-5-15:2022, flat-band voltage, electroreflectance spectroscopy, ER spectroscopy, GaN-based LED, internal electric field, test method, LED characterization.
Open preview (PDF)Semiconductor devices - Part 5-15: Optoelectronic devices - Light emitting diodes - Test method of the flat-band voltage based on the electroreflectance spectroscopy
