We report on the use of a novel technique to study reactive ion etching (RIE) induced damage using multiple quantum wens of 20-, 40-, 60-, and 90-A widths as in situ probes. Cathodoluminescence (CL) at low temperature, using a finely focused electron beam, allows sensitive determination of the quality of individual quantum wens before and after RIE damage. There is a correspondence between individual luminescence peaks and the depth of the particular quantum well. We can therefore use the CL spectral information to provide a sensitive profile of the depth of RIE induced damage. Various etching conditions and the effects of postetch anneals are examined. Pure Ar sputtering and enhanced chemical etching using CCI 2 F 2 /BCI 3 at different bias voltages are investigated. Our results reveal that the degree and spatial extent of damage increase with increasing ion energy and decreasing ion mass.

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This work presents etch rate versus temperature data for GaAs and InP etched by Cl2 and HCl both with and without a remote plasma. The data is described both qualitatively and quantitatively by a thermodynamic model utilizing reactant-flux-limited and product-desorption-limited regimes. This ‘‘ionless’’ etching technique demonstrates reactant-flux-limited, temperature-independent behavior for HCl etching of GaAs for over five orders of magnitude of flux. InP and GaAs show nearly equirate etching at T>150 °C with both gases. Reactive ion etching (RIE) with Cl2 of InP at elevated temperatures produces only moderate rate enhancements; RIE gave a maximum etch rate of ∼800 Å/min at 175 °C compared to ∼0.5 μm/min obtained with the remote plasma system at the same temperature.

The photochemistry of quadricyclane (Q) was explored by single-photon excitation to high vibrational levels. Spectra of the u = 4-7 carbon-hydrogen overtones were recorded by using intracavity absorption and photoacoustic detection. These spectra were compared to the infrared fundamental spectrum and assigned. Excitation of the v = 5 and v = 6 bands of cyclopropanoid and methylenic hydrogens leads to reaction. At least one intermediate, probably a vibrationally excited form of norbornadiene (N), must be involved because partitioning among various reaction channels is pressure dependent. Apparent rate constants were measured and correlated with variations in pressure according to the Stem-Volmer relationship. Experimental values were compared with rate constants calculated by RRKM theory. Although there is a modest amount of Uexcess" reaction observed for the lowest excitation energies above threshold, overall evaluation provides no significant evidence for concentration of energy in localized modes for times that are long compared with reaction times.

Raman scattering spectroscopy is used to probe the surface electrical properties (surface depletion width) of GaAs after dry etching in either a reactive ion etching (RIE) system or a remote plasma system. A variety of etch gases (argon, helium, Freon 12, HCl) and biases (−80 to −350 V) are used to examine physically and chemically induced damage. Through the use of wet etches, the dry etch induced damage was observed to be within ∼300 Å of the surface. In the RIE system, etching with argon and helium causes the depletion width to widen, with helium inducing a greater effect. A remote plasma does not cause a change in the depletion width, indicating an absence of energetically damaging species. In contrast to inert gases, etching with reactive gases in both systems reduces the effective surface charge.