However, it remains elusive to achieve nonpolar/semipolar substrates with good quality and low cost. Extensive efforts have been devoted to the development of nonpolar/semipolar III-nitride optoelectronics 16– 20. To date, however, it has remained a daunting challenge to achieve such µLEDs, especially in the emission wavelength range of green/red.Ĭonventional InGaN quantum well (QW)-based LEDs suffer from wavelength/color instability due to the quantum-confined Stark effect (QCSE), which manifests itself as a severe wavelength blue-shift with increasing optical excitation or electrical injection 13– 15. It is desired that the micro, or submicron scale LEDs (µLEDs) can exhibit highly stable emission, high efficiency and brightness, ultralow power consumption, and full-color emission, and can be monolithically grown on Si for integration with complementary metal-oxide-semiconductor (CMOS) electronics. For the emerging revolution in augmented reality (AR)/mixed reality (MR), however, LEDs with dimensions as small as one micrometer, i.e., LEDs with a surface area approximately one million times smaller than conventional broad area devices, are in demand 1– 12. The past two decades have witnessed the solid-state lighting revolution powered by GaN-based broad area light-emitting diodes (LEDs), which generally have lateral dimensions on the order of millimeters. This study provides new insights and a viable path for the design, fabrication, and integration of high-performance µLEDs on Si for a broad range of applications in on-chip optical communication and emerging augmented reality/mixed reality devices, and so on. In comparison with conventional GaN barriers, AlGaN barriers are shown to effectively compensate for the tensile strain within the active region, which significantly reduces the strain distribution and results in enhanced indium incorporation without compromising the material quality. Detailed elemental mapping and numerical calculations show that the QCSE is screened by introducing polarization doping in the active region, which consists of InGaN/AlGaN QWs surrounded by an AlGaN/GaN shell with a negative Al composition gradient along the c-axis. The µLEDs feature ultra-stable, bright green emission with negligible quantum-confined Stark effect (QCSE). Here we report, for the first time, µLEDs grown directly on Si with submicron lateral dimensions. The etching-induced surface damages and poor material quality of high indium composition InGaN quantum wells (QWs) severely deteriorate the performance of µLEDs, particularly those emitting in the green/red wavelength. The polar nature of III-nitrides causes severe wavelength/color instability with varying carrier concentrations in the active region. Achieving such µLEDs, however, has remained a daunting challenge. It is desired that µLEDs exhibit high stability and efficiency, submicron pixel size, and potential monolithic integration with Si-based complementary metal-oxide-semiconductor (CMOS) electronics. Micro or submicron scale light-emitting diodes (µLEDs) have been extensively studied recently as the next-generation display technology.
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