Influence of the epitaxial composition on N-face GaN KOH etch kinetics determined by ICP-OES.

Markus Tautz,Martin Welzel,Robert Weinberger,Joachim Hertkorn,Maren T Kuchenbrod,David Díaz Díaz,Arno Pfitzner

doi:10.3762/bjnano.11.4

Abstract

Roughening by anisotropic etching of N-face gallium nitride is the key aspect in today’s production of blue and white light emitting diodes (LEDs). Both surface area and number of surface angles are increased, facilitating light outcoupling from the LED chip. The structure of a GaN layer stack grown by metal organic chemical vapour deposition (MOCVD) was varied in the unintentionally doped u-GaN bulk region. Different sequences of 2D and 3D grown layers led to a variation in dislocation density, which was monitored by photoluminescence microscopy (PLM) and X-ray diffraction (XRD). Thin-film processing including laser lift off (LLO) was applied. The influence of epitaxial changes on the N-face etch kinetics was determined in aqueous KOH solution at elevated temperature. Inductively-coupled plasma optical emission spectroscopy (ICP-OES) was used to measure the etch progress in small time increments with high precision. Thereby, the disadvantages of other techniques such as determination of weight loss or height difference were overcome, achieving high accuracy and reproducibility.

Highlights

The light emitting diode (LED) has become the basis of modern energy-efficient lighting technology over the last 30 years [1]
Different sequences of 2D and 3D grown layers led to a variation in dislocation density, which was monitored by photoluminescence microscopy (PLM) and X-ray diffraction (XRD)
Fourfold Inductively-coupled plasma optical emission spectroscopy (ICP-OES) analysis of an identical KOH dilution stemming from a single gallium nitride (GaN) chip etched at RT for 1 h yielded 249 ± 3 nm average GaN removal and a relative error of 1%

Summary

Introduction

The light emitting diode (LED) has become the basis of modern energy-efficient lighting technology over the last 30 years [1]. The binary III–V semiconductor gallium nitride (GaN) is very useful for consumer lighting application. The high band gap energy of 3.4 eV at room temperature permits the production of blue and phosphor-converted white LEDs [2]. To reach a high internal quantum efficiency (IQE), crystal quality must be high in terms of low dislocation density [3]. Dislocations cause non-radiative recombination of induced electron hole pairs and lower efficiency.

Methods

Results

Conclusion