In the present paper the electroluminescence of PIN diodes with either stra
ined SiGe/Si or Ge islands in the i-region has been investigated experiment
ally and by quantitative modelling. The modelling helped to improve the dio
de structure. Consequently, diodes with strained Si0.80Ge0.20 could be impr
oved so as to reveal emission up to room temperature, if the thickness was
high enough. To overcome the thickness limitation due to plastic relaxation
, we used selective epitaxy on small areas. We also present results for dio
des with Ge islands in the active region. The internal quantum efficiency o
f light emitting diodes with strained SiGe was at room temperature similar
to 10(-4), while diodes with islands emitted ten times less light. (C) 1999
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