The feasibility of producing erbium-doped silicon light-emitting diodes by molecular beam epitaxy is demonstrated. The p-n junctions are formed by growing an erbium-doped p-type epitaxial silicon layer on an n-type silicon substrate. When the diodes are biased in the forward direction at 77 K they show an intense sharply structured electroluminescence spectrum at 1.54 μm. This luminescence is assigned to the internal 4f–4f transition 4I13/2→4I15/2 of Er3+ (4f11).

SF6 is a far more selective etchant for silicon than CF4+O2 when excited to a plasma discharge. This applies to good advantage in parallel plate reactors where under given conditions of rf power and pressure the etch ratio of silicon to SiO2 is 30:1 but with CF4 only 7:1. In contrast to the deposition of carbon in a CF4 process sulfur has not been found on a silicon surface etched in SF6 . The selectivity of an SF6 etching process cannot be shifted sufficiently in favor of SiO2 by adding hydrogen, it can also not be increased much in favor of silicon by adding oxygen. The reaction product is SiF4 . No other silicon compound than SiF3 + appeared in the mass spectrum. 1% SF6 in argon achieves etch rates of more than 100 nm/min with moderate rf energy. SF6 is also a useful etchant for Si3N4 with etch rates of 100 nm/min.

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By means of a resistance thermometer structure diffused into the surface of a silicon wafer the temperature has been found to increase within a minute to over 100°C in a CF4 plasma. In contrast the system temperature rises only about 5 °C in the same time. This applies to a system in the tunnel configuration. In a parallel plate system the rise is far less steep and even within the usual etching time an equilibrium temperature is reached. The dependence of the etch rate on the surface temperature has been measured. In the interval from R.T. and 100 °C the etch rate stays nearly the same. Therefore temperature is no significant parameter for establishing desired etch rates