Inductively coupled plasma etching of InP using HBr/O 2 -based chemistry is reported. With the introduction of oxygen in the HBr plasma, high etching rate, smooth surface morphology, and vertical sidewall profile were achieved due to sidewall passivation and enhancement of ion-assisted chemical etching. The etching behavior was systematically studied by varying different process parameters, i.e., O 2 flow rate, pressure, reactive ion etching power, and inductively coupled plasma power, in a ridge array structure with a ridge width of 1 m and a ridge spacing of 1 m. InP nanopillars with an aspect ratio of ϳ6.7 were demonstrated using this chemistry. The X-ray photoelectron spectroscopy results suggested that the etched sample surface was P-rich.Plasma etching has the advantages over chemical etching for the possibility of obtaining an anisotropic etching profile and better uniformity over the entire wafer. InP has been used extensively for the fabrication of various photonic devices, such as semiconductor lasers with an emission wavelength around ϳ1.55 m for optical communication purpose. High aspect ratio etching is often required for photonic crystals, distributed Bragg reflectors, ridge structures, etc. The critical part in realizing high aspect ratio etching is to get a straight vertical profile. Most of the plasma etchings for InP-based material systems employ either CH 4 /H 2 -or Cl 2 -based chemistries. 1-3 Etching of InP using CH 4 /H 2 is complicated because of the slow etching rate, indium enrichment, and polymer formation. 4 A substrate temperature over 200°C is required to produce highly anisotropic sidewalls using Cl 2 -based chemistry. 5 Thus, there is a strong motivation to find an alternative chemistry to achieve a better control of the etching properties. There were reports on inductively coupled plasma ͑ICP͒ etching of InP using HBr-based chemistry. 4,6-8 Bromine-based chemistry has the advantage that the reaction product, InBr 3 , has a higher vapor pressure than that of InCl 3 when using chlorine-based chemistry. 5 Furthermore, GaBr 3 and InBr 3 have a more closely matched function of vapor pressures vs temperature as compared to their chloride counterparts. This property is beneficial for the fabrication of photonic devices that often require the etching of InGaAsP quaternary materials. Several methods had been tried to improve the InP ICP etching properties using HBr chemistry. For example, Ar was mixed with HBr to improve the anisotropy of InP etching at room temperature. 6 CH 4 and N 2 were added into the plasma to passivate the sidewall and reduce the undercuts that were observed when using HBr only at elevated temperature. 4,7,8 Recently, a Cl 2 /O 2 mixture in ICP etching of InP was reported to be able to produce a highly anisotropic profile. 9 In this paper, we report the use of HBr/O 2 chemistry for the etching of InP to achieve high aspect ratio and no undercut in an ICP etching system. The etching behavior was systematically studied by varying different process parameters, i.e., O 2 ...

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One challenge in fabricating submicron ridge waveguide photonic devices is the formation of metal contacts and passivation. In this article, the authors report a self-aligned metal-contact and passivation technique suitable for submicron to nanoscale ridge waveguide device fabrication. The technique uses two different dielectric materials, e.g., SiO2 and Si3N4, with a different wet-etching selectivity. The first dielectric material (SiO2) acts as the etching mask and the second dielectric material (Si3N4) with a much lower etching rate acts as the passivation film. An undercut is formed in the semiconductor below the SiO2 mask by a wet-etching process. The semiconductor surface on top of the ridge waveguide will be fully exposed to metal contact by the lift-off process. A 0.7-μm-wide InGaAsP∕InP ridge waveguide laser was fabricated using the technique proposed. Mode simulation showed that the 0.7-μm-wide and 1.2-μm-deep ridge waveguide in the InGaAsP∕InP laser structure has good optical field confinement. Lasing is obtained on the 0.7-μm-wide ridge waveguide laser under current injection. An ∼240nm ridge waveguide is also demonstrated as an example of the technology for deep-submicron waveguide structure fabrication. The whole process is completely compatible with the existing compound semiconductor process and can be extended to fabricating other submicron to nanoscale devices.