(Invited) Realization of Stable Electrical Performance of Algainp-Based Red Micro-Light-Emitting Diode By Controlling Interfacial Morphologies of Metal Contacts

Abstract

The stable electrical performance of micro-light-emitting diodes (micro-LEDs) is critical to display application. For micro-display application, the development of high-efficiency full color micro-LEDs (e.g., red, green, and blue emitters) is critical. In particular, despite the importance for the realization of high-efficiency red emitters, AlGaInP-based micro-LEDs have not been extensively investigated yet. Use of contacts to an n-AlInP layer can be effective in reducing the thickness of the epilayers and in improving the performance of red micro-LEDs.We investigated the effect of the interface morphologies of contacts to n-AlInP on the electrical stability of AlGaInP-based red micro-LEDs. After annealing, for the AuGe/Ni/Au contacts, heavily inhomogeneous interfacial reactions occurred across the whole contact/AlInP interface, whereas the Pd/Ge contacts showed relatively similar interfacial morphologies. Regardless of chip sizes (100 μm or 10 μm-size), micro-LEDs with Pd/Ge contacts gave lower and stable forward voltages than those with AuGe/Ni/Au contacts; the average forward bias voltages of the 10 and 100 μm-size micro-LEDs were 3.04 and 3.89 V at 50 A/cm2 for the AuGe/Ni/Au contact, respectively, and 2.08 and 2.7 V and Pd/Ge contact. Further, irrespective of the chip sizes, the micro-LEDs with the Pd/Ge contacts experienced less operation-time-induced degradation than the ones with the AuGe/Ni/Au contacts. Based on the STEM and electrical results, the spread of the forward voltages of micro-LEDs was explained in terms of the inhomogeneously reacted interfacial morphologies of AuGe/Ni/Au contacts to AlInP. The results indicate that the Pd/Ge contact can serve as a promising contact to n-AlInP for high-performance AlGaAsP-based red emitters for display application.