Wuhan University team's new research: red Mini LED efficiency increased by 30%

Recently, Zhou Shengjun's team at Wuhan University developed a new Schottky-contact intrinsic current blocking layer (SCBL), which can enhance current diffusion in the active region. And improve the light extraction efficiency of AlGaInP red Mini LED (LEE).

The above diagram shows (a) the device structure, and (b) the manufacturing process based on AlGaInP's red light vertical structure Mini LED with SCBL. (c) SCBL and (d) AlGaInP based red light vertical structure Mini LED top view optical microscope images.

Research leader Shengjun Zhou said that the team used the Schottky contact properties between indium tin oxide (ITO) and p-GaP, as well as the ohmic contact properties between ITO and p-GaP+ to construct the SCBL, which was demonstrated by the transfer length method.

Zhou Shengjun said that SCBL can effectively alleviate the current crowding around the p electrode and promote uniform current diffusion, thereby improving the light extraction efficiency of AlGaInP red Mini LED. Due to enhanced current diffusion and light extraction, Mini leds with SCBL show a more uniform distribution of luminous intensity, higher optical output power, and higher external quantum efficiency (EQE).

AlGaInP red Mini LED is widely used as an important part of full-color displays due to its high brightness, low energy consumption and long service life.

However, current crowding around the p electrode results in uneven current distribution in the active region. In addition, because most of the photons generated in the active region are absorbed or reflected by the opaque metal p electrode, the light extraction efficiency (LEE) of the AlgainP-based Mini LED is low.

To solve this problem, the researchers introduced SCBL to improve the current diffusion and light extraction of AlgainP-based Mini leds. By using Schottky contacts between ITO and P-gap, SCBL can prevent current crowding around the p electrode. The current is forced into the active region through the P-GAP + ohmic contact layer to avoid the absorption and reflection of light by the opaque metal p electrode.

The results showed that the external quantum efficiency (EQE) of an AlGaInP based Mini LED using SCBL can be increased by up to 31.8% at a current of 20mA compared to an AlGaInP based Mini LED without SCBL. Therefore, the SCBL technology is expected to be applied to the mass production of efficient AlgainP-based red Mini LED in the future.

It is worth noting that the Zhou Shengjun team of Wuhan University has also released a number of new LED research results. For example, in the field of deep ultraviolet leds, the team introduced the Algan-based ultra-thin tunnel junction (26 nm) in the deep ultraviolet LED, which increased the electro-optical conversion efficiency of the deep ultraviolet LED by 5.5%.

In the field of Mini LED, the team improved the performance of blue and green flip Mini LED chips by using a Full-angle Distributed Bragg Reflector (DBR). Under the condition of 10mA injection current, the optical output power of blue and green Mini LED based on ITO/DBR is increased by about 7.7% and 7.3%, respectively.