Wuhan team improves red mini-LEDs
Researchers from Wuhan University in China have reported a novel Schottky-contact intrinsic current blocking layer (SCBL) to enhance current spreading in active region and to boost light extraction efficiency (LEE) of AlGaInP-based red mini-LEDs.
“We construct a SCBL by utilising the Schottky contact characteristic between Indium-tin-oxide (ITO) and p-GaP as well as the ohmic contact characteristic between ITO and p-GaP+, which is demonstrated by using transfer length method," said Shengjun Zhou, who directed the research.
He added: "The SCBL can effectively alleviate the current crowding around p-electrode and facilitate uniform current spreading, thereby boosting the LEE of AlGaInP-based red mini-LEDs. Owing to the enhancement of current spreading and light extraction, the mini-LED with SCBL reveals more uniform light emission intensity distribution, improved light output power, and higher external quantum efficiency (EQE), in comparison with the mini-LED without SCBL.”
AlGaInP-based red mini-LEDs have been widely applied as the essential component of full-color display due to their high luminance, low energy consumption, and long operating lifetime. However, current crowding issue around the p-electrode causes the inhomogeneous distribution of current across active region. A large portion of photons generated from active region are absorbed or reflected by the opaque metal p-electrode, resulting in low LEE of AlGaInP-based mini-LEDs.
To address the issue, the researchers introduce a SCBL to improve current spreading and light extraction of AlGaInP-based mini-LEDs. By using Schottky contact between ITO and p-GaP, the SCBL can hinder current crowding around p-electrode. The current is forced to inject into active region through p-GaP+ ohmic contact layer, avoiding light absorption and reflection by the opaque metal p-electrode. As a result, the AlGaInP-based mini-LED with SCBL reveals an increment of EQE up to 31.8 percent at 20 mA, as compared with the AlGaInP-based mini-LED without SCBL. The SCBL technology is promising towards the applications in mass production of high-efficiency AlGaInP-based red mini-LEDs.
Pictured above (a) Device structure, and (b) fabrication process flow of AlGaInP-based red vertical mini-LED with SCBL. Top-view optical microscopy image of (c) SCBL and (d) AlGaInP-based red vertical mini-LED.
Reference
‘Schottky-contact intrinsic current blocking layer for high efficiency AlGaInP-based red mini-LEDs’ by Shengjun Zhou et al; Optics Letters 49(13): 3765 (2024)
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