Thermally stable and highly reflective AgAl alloy for enhancing light extraction efficiency in GaN light-emitting diodes

Abstract

The properties of a AgAl alloy reflector layer deposited on a p-GaN layer for use in high-efficiency GaN flip-chip light-emitting diodes (FCLEDs) were investigated. The AgAl layer showed good adhesion properties compared to a layer of Ag on p-GaN. In addition, no agglomeration was found, indicating that the AgAl layer is thermally stable due to the formation of oxidized Al on the surface and at the interface of the AgAl layer. The InGaN∕GaN multiquantum well light-emitting diode with the annealed AgAl layer showed good I-V characteristic and an enhanced optical output power compared to that with an annealed Ag layer due to the high reflectivity (86.7% at 465 nm), smooth surface after annealing, and good Ohmic property of AgAl. These results clearly indicate that a AgAl layer on p-GaN constitutes a promising reflector and Ohmic scheme for achieving high-brightness FCLEDs.

Strain induced suppression of silver agglomeration of indium-containing silver contact

“…1 In these configurations, Ag has been widely used for a reflective Ohmic contact due to its high reflectance ͑Ͼ95%͒ for visible light. 3,4 Preventing Ag contacts from agglomeration is a key aspect in obtaining high quality Agbased Ohmic contacts. 3,4 Preventing Ag contacts from agglomeration is a key aspect in obtaining high quality Agbased Ohmic contacts.…”

“…3,4 Preventing Ag contacts from agglomeration is a key aspect in obtaining high quality Agbased Ohmic contacts. 3,6 The Ag alloys with a slowdiffusing species and the Pt capping layer were effective in suppressing the grain boundary grooving to enhance the thermal stability. 4,5 Several kinds of attempts to improve thermal stability of the Agbased contacts have been proposed such as the surface passivation of Ag contacts with Al oxides and the segregation of Cu oxides in Ag contacts.…”

Enhanced light extraction efficiency in flip-chip GaN light-emitting diodes with diffuse Ag reflector on nanotextured indium-tin oxide

“…However, a Ag shows very poor adhesion and thermal characteristics. [12][13][14][15] To solve these problems, transparent layers inserted between the Ag reflector and p-GaN, 12,13 Ag-based alloy layers such as AgAl alloy layer, 14 and AgCu alloy layer 15 have been introduced. However, these studies were based mainly on a Ag reflector layers deposited on the planar surface of transparent conducting layers or p-GaN.…”

Effect of oxygen plasma treatment on nonalloyed Al/Ti-based contact for high power InGaN/GaN vertical light-emitting diodes

“…[16][17][18] One of the promising metal reflectors involves aluminum (Al). 19 While it is an inexpensive metal and easily formed by an evaporator or a sputter system, there is a drawback such as poor contact resistance as compared to Cr-based contact. In this study, we report on electrical and optical characteristics for vertical InGaN/GaN LED structure with Al/Tibased n-metals as well as the conventional Cr/Au metals.…”