Abstract
We report the fabrication and studies of electrically driven green, olivine, and amber color nanopyramid GaN light emitting diodes (LEDs). InGaN/GaN multiple quantum wells (MQWs) were grown on the nanopyramid semipolar facets. Compared with the commonly used (0001) c-plane MQWs, the semipolar facet has lower piezoelectric field, resulting in much faster radiative recombination efficiency. This is important for high In content MQWs. The measured internal quantum efficiencies for green, olivine, and amber color LED are 30%, 25%, and 21%, respectively. The radiative and non-radiative lifetime of the semipolar MQWs are also investigated.
Highlights
The III-nitride based light emitting diodes (LEDs) has gained great research interests due to its promising potential in high efficient lighting applications
The high resolution tunneling electron microscope (HRTEM) image taken by a JEOL JEM-2100 electron microscope at 200KV is shown in Fig. 1(e), showing the multiple quantum wells (MQWs) grown on the inclined pyramid facets
The decrease in efficiency as the sample changes from G- to A-LED is because the increase of In content induces larger internal polarization field which results in larger electron-hole wave function separation
Summary
The III-nitride based LED has gained great research interests due to its promising potential in high efficient lighting applications. Experimental demonstrations have shown improved emission efficiency for MQWs grown on semipolar and nonpolar substrates [6,7,8]. The peak emission wavelengths of these samples monotonically decrease with increasing temperature, indicating less localized potential [15,16,17,18] which causes faster non-radiative lifetime. The internal quantum efficiencies (IQEs) of the green, olivine, and amber color LED are 30%, 25%, and 21%, respectively, which are hard to achieve for cplane MQWs in the same wavelength range. The efficiency decrease is attributed to the increase of piezoelectric field in MQWs as In content increases
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