Performance Improvement of GaN Based Laser Diode Using Pd/Ni/Au Metallization Ohmic Contact

Abstract

We report an investigation of the effects of different metal systems and surface treatment on the contact performance of GaN lasers. We found that multi-element metal alloy and surface chemical treatment are the keys to achieve good ohmic behavior contacts on GaN laser diodes. Pd/Ni/Au contact demonstrates excellent thermal stability and lowest specific contact resistivity in these metal systems. Properly adjusting the thickness of the Pd and Ni layer and pretreating with the KOH solution can further improve the ohmic contact performance. The improved ohmic behavior of the KOH solution pretreated Pd/Ni/Au contact is attributed to removing surface oxides and the reduction of the schottky barrier heights due to the metal Pd has a high work function and the interfacial reactions occurring between the Pd, Ni, Au, and GaN extends into the GaN film. As a result, a low contact resistivity of 1.66 × 10−5 Ω·cm2 can be achieved from Pd(10 nm)/Ni(10 nm)/Au(30 nm) contacts with KOH solution pretreated on top of the laser diode structure. The power of the GaN based laser diode with the Pd/Ni/Au metallization ohmic contact can be enhanced by 1.95 times and the threshold current decreased by 37% compared to that of the conventional ohmic contact Ni/Au.

Properties of Bare and Thin-Film-Covered GaN(0001) Surfaces

“…Due to one of the highest work function values among metallic elements, both Ni and Pd are used as materials or components for making electrical contacts with GaN. Electric contacts using Pd/Ni bilayers improve device performance [32]. The interfacial reaction between nickel and GaN can occur during annealing [33], which is a commonly used step for contact creation.…”

Effects of AlInGaN electron barrier layer with different aluminum components on the photoelectric properties of GaN-based laser

“…In recent decades, GaN-based laser diode has become a research interest in laser field due to its extensive applications in laser display, material processing, information storage, laser communication and other fields [1][2][3][4]. With the continuous improvement of epitaxial material growth technology, the photoelectric performance of GaN-based lasers has been greatly improved.…”

Enhancing performance of GaN-based LDs by using GaN/InGaN asymmetric lower waveguide layers

“…With the advantages of small size, high efficiency, long life, and fast response speed, GaN-based semiconductor laser is widely used in laser display, laser lighting, underwater communication, biomedicine, and other civil and military fields. [1][2][3][4][5][6][7][8] In particular, the GaN-based violet laser diodes (LDs) have attracted attention as a new laser source for high-density optical disk storage. [9,10] To realize such applications, high power GaN LD is significantly important.…”