Wafer-scale GaN DBRs via electrochemical porosification

Start date January 2018

Cambridge University

Client University of Cambridge
Investigator

Dr David Nugent
david.nugent@elucidare.co.uk

 


Abstract

Distributed Bragg reflectors (DBRs) are essential components for the development of optoelectronic devices. For many device applications, it is highly desirable to achieve not only high reflectivity and low absorption, but also good conductivity to allow effective electrical injection of charges. Researchers from Cambridge University have demonstrated the wafer-scale fabrication of highly reflective and conductive non-polar gallium nitride (GaN) DBRs, consisting of perfectly lattice-matched non-polar (11–20) GaN and mesoporous GaN layers that are obtained by a facile one-step electrochemical etching method without any extra processing steps. The GaN/mesoporous GaN DBRs exhibit high peak reflectivities (>96%) across the entire visible spectrum and wide spectral stop-band widths (full-width at half-maximum >80 nm), while preserving the material quality and showing good electrical conductivity. Such mesoporous GaN DBRs thus provide a promising and scalable platform for high performance GaN-based optoelectronic, photonic, and quantum photonic devices.

 

  Electrochemical-etching-GaN-DBR

 

Figure 1: Schematic of the experimental setup for the EC etching and a photograph of a sample afer the etching under room light illumination. (b) Schematic of the DBR structure. (c) Cross-sectional SEM image of the 10 pair GaN/MP-GaN DBR structure.

 

ExperimentalDBRreflectivityMeasurement

 

Figure 2: (a) Experimental (red dash line), transfer matrix method (blue solid line), and fnite element method simulated (black solid line) reflectance spectra from the GaN/MP-GaN DBR structure. Te reflectance spectra of the unetched sample (green solid line) and the sapphire substrate (orange solid line) are also shown for comparison. (b) Electric feld distribution in a GaN/MP-GaN DBR with real pore morphology inputted by digitising the SEM image shown in Fig. 2b into the fnite element model. (c) Photograph of an as-etched 2-inch mesoporous GaN DBR wafer reflecting a card with the Cambridge University Logo.

 

Documents available for download

Technology summary
Wafer-scale Fabrication of Non-Polar Mesoporous GaN Distributed Bragg Reflectors via Electrochemical Porosifcation - Nature Paper click here