Realization and optical characterization of etched mirror facets in GaN cavities

Ga+ and Au+ focused ion beams (FIB) are used to micromachine GaN films. The GaN micromachining has been studied at energies from 30-90 keV, incident angle from 0-30°, and number of repetitive scans from 10 to 50 scans. Trenches milled in GaN have vertical and smooth side-walls and very smooth bottoms. The micromachining rate was found to be fairly independent of ion dose, ranging from 0.4 to 0.6 µm3/nC for Ga+ and 1 to 2 µm3/nC for Au+. This translates into an effective yield of of 6-7 atoms/ion for Ga+ and 21-26 atoms/ion for Au+. This represents the highest direct FIB removal yield reported to date. We have also investigated the micromachining of GaN substrate material: c-face sapphire. Using FIB Ga+, sapphire has an effective yield of ∼2-2.5 atoms/ion, or approximately 1/3 of the GaN sputtering yield. For the materials investigated, we found the sputtering yield to be inversely proportional to the strength of the material chemical bond. We also describe the application of the FIB μmachining technique to the fabrication of small period Distributed Bragg Reflector (DBR) mirrors for a short cavity GaN laser structure.

Section: Introductionmentioning

confidence: 99%

Focused Ion Beam Micromachining of GaN Photonic Devices

Chyr

Steckl

1999

“…However, the etch rates for x < 0.1 were not significantly different, therefore heterostructures such as those utilized for lasers can essentially be etched at equi-etch rates. Ar/Cl 2 CAIBE etching produced anisotropic but only near-vertical etch profiles [9,31] at all substrate temperatures. The profiles were more vertical at higher temperatures due to increased chemical activities during etching [8,9].…”

Section: Etch Rates and Profilesmentioning

confidence: 99%

“…The profiles were more vertical at higher temperatures due to increased chemical activities during etching [8,9]. In order to achieve the verticality necessary for laser facets, Binet [31] and Kneissl et al [30] tilted and rotated their samples while etching. InGaN/AlGaN laser diodes with CAIBE-etched facets have been fabricated and demonstrated using this method by Kneissl et al [30].…”

Section: Etch Rates and Profilesmentioning

confidence: 99%

Dry and Wet Etching for Group III – Nitrides

Adesida

Youtsey

Ping

et al. 1999

The group-III nitrides have become versatile semiconductors for short wavelength emitters, high temperature microwave transistors, photodetectors, and field emission tips. The processing of these materials is significant due to the unusually high bond energies that they possess. The dry and wet etching methods developed for these materials over the last few years are reviewed. High etch rates and highly anisotropic profiles obtained by inductively-coupled-plasma reactive ion etching are presented. Photoenhanced wet etching provides an alternative path to obtaining high etch rates without ion-induced damage. This method is shown to be suitable for device fabrication as well as for the estimation of dislocation densities in n-GaN. This has the potential of developing into a method for rapid evaluation of materials.

“…1,2 There are several disadvantages to dry etching, including the generation of ion-induced damage 3 and difficulty in obtaining smooth etched sidewalls, which are required for lasers. The typical root-mean-square (RMS) roughness of sidewalls produced by dry etching is on the order of 50 nm, 4,5 although recently surfaces with an RMS roughness as low as 4-6 nm have been reported. 6 Photoenhanced electro-chemical (PEC) wet etching has also been demonstrated for etching of GaN.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Smooth GaN-Based Laser Facets

Stocker

Schubert

Boutros³

et al. 1999

A method is presented for fabricating fully wet-etched InGaN/GaN laser cavities using hotoenhanced electrochemical wet etching followed by crystallographic wet etching. Crystallographic wet chemical etching of n- and p-type GaN grown on c-plane sapphire is achieved using H3PO4 and various hydroxides, with etch rates as high as 3.2.μm/min. The crystallographic GaN etch planes are {0001}, {100}, {10}, {10}, and {103}. The vertical {100} planes appear perfectly smooth when viewed with a field-effect scanning electron microscope (FESEM), indicating a surface roughness less than 5 nm, suitable for laser facets. The etch rate and crystallographic nature for the various etching solutions are independent of conductivity, as shown by seamless etching of a p-GaN/undoped, high-resistivity GaN homojunction.