Increased Light Extraction with Multistep Deposition of ZnO on GaN

Brief Description

A method of depositing ZnO on III-nitride materials using a multistep approach involving the deposition of a thin seed layer followed by the deposition of a thicker bulk layer.

Background

Conductive Zinc Oxide (ZnO) films are especially well suited for application as transparent electrodes on III-nitride-based optoelectronics. Given that ZnO and III-N materials share the same wurtzite crystal structure and are closely lattice matched to one another, epitaxial films of ZnO can be deposited on this material system. This allows for the growth of ordered crystalline ZnO films with high carrier mobilities and low optical absorbance, due to the reduction of photon/electron scattering centers such as grain boundaries, point defects, and lattice distortions. In addition, ZnO’s high refractive index of ~2 allows for more efficient light extraction from III-N light emitters such as GaN, whose refractive index is ~2.5, by increasing the critical angle for total internal reflection. Moreover, the ease of pattern ability, whether through selective area growth, patterned etching, or roughening etches, further increases light extraction.

Description

UC Santa Barbara researchers have developed a method of depositing ZnO on III-nitride materials using a multistep approach involving the deposition of a thin seed layer followed by the deposition of a thicker bulk layer. This method yields high quality films and can be employed on a wide scale. It also allows for ZnO to compete with materials such as indium tin oxide (ITO) as a transparent conducting oxide for optoelectronic applications such as III-nitride light emitters and photovoltaics.

Advantages

• High quality films
• More efficient light extraction

Applications

• Optoelectronic applications
• III-nitride light emitters and photovoltaics

Patent Status