Tellurium-modified silicon nanowires with a large negative temperature coefficient of resistance Appl. Phys. Lett. 101, 133111 (2012) Tapered and aperiodic silicon nanostructures with very low reflectance for solar hydrogen evolution Appl. Phys. Lett. 101, 133906 (2012) Minimizing scattering from antireflective surfaces replicated from low-aspect-ratio black silicon Appl. Phys. Lett. 101, 131902 (2012) Robust hydrophobic Fe-based amorphous coating by thermal spraying Appl. Phys. Lett. 101, 121603 (2012) Influence of high temperature on solid state nuclear track detector parameters Rev. Sci. Instrum. 83, 093502 (2012) Additional information on Appl. Phys. Lett.

A parametric study of the etch characteristics of Ga-based (GaAs, GaSb, and AlGaAs) and In-based (InGaP, InP, InAs, and InGaAsP) compound semiconductors in BCl 3 /Ar planar inductively coupled plasmas (ICPs) was performed. The Ga-based materials etched at significantly higher rates, as expected from the higher volatilities of the As, Ga, and Al trichloride, etch products relative to InCl 3 . The ratio of BCl 3 to Ar proved critical in determining the anisotropy of the etching for GaAs and AlGaAs, through its effect on sidewall passivation. The etched features in In-based materials tended to have sloped sidewalls and much rougher surfaces than for GaAs and AlGaAs. The etched surfaces of both AlGaAs and GaAs have comparable root-mean-square (RMS) roughness and similar stoichiometry to their unetched control samples, while the surfaces of In-based materials are degraded by the etching. The practical effect of the Ar addition is found to be the ability to operate the ICP source over a broader range of pressures and to still maintain acceptable etch rates.

We investigated dry etching of GaAs in a planar inductively coupled plasma ͑ICP͒ reactor with BCl 3 gas chemistry. The process parameters included planar ICP source power, chamber pressure, reactive ion etching ͑RIE͒ chuck power, and gas flow rate. The ICP source power was varied from 0 to 500 W. Chamber pressure was changed from 5 to 20 mTorr. RIE chuck power was controlled from 0 to 150 W. The gas flow rate was varied from 10 to 40 sccm. We found that a process condition at 20 sccm BCl 3 , 300 W ICP, 100 W RIE, and 7.5 mTorr chamber pressure gave an excellent etch result. The etched GaAs feature showed extremely smooth surface (rms roughness Ͻ 1 nm), vertical sidewall, relatively fast etch rate ͑Ͼ3000 Å/min͒ and good selectivity to a photoresist ͑Ͼ3:1͒. X-ray photoelectron spectroscopy study on the surface of processed GaAs proved a very clean surface of the material after dry etching. We also noticed that our planar ICP source was successfully ignited both with and without RIE chuck power, which was generally not the case with a typical cylindrical ICP source, where assistance of RIE chuck power was required for turning on a plasma and maintaining it. These results indicate that the planar ICP source could be a very versatile tool for advanced dry etching of damage-sensitive compound semiconductors.

We developed optical emission spectroscopy based end-point detection techniques for GaAs-based etching in inductively coupled BCl 3 /N 2 plasmas. It was found that an emission peak of Ga ͑417 nm͒ was quite useful as a tracer for in situ process monitoring during both AlGaAs/GaAs and InGaP/GaAs multilayer etching. The intensity of the Ga emission peak increased significantly during AlGaAs/GaAs etching in a BCl 3 /N 2 inductively coupled plasma when the GaAs layer was exposed to the plasma. We found the same result with InGaP/GaAs etching. Utilization of the Ga peak signal is very important during the plasma process for GaAs-based device fabrication, especially for high electron mobility transistors and heterojunction bipolar transistors in order to minimize overetch time during the nonselective etching. The technique provides a breakthrough for in situ end-point detection of GaAs-based nonselective plasma etching.