Electroluminescence of n-Ge/i-Ge/p-Si heterojunction PIN LEDs

A PIN Light Emitting Diode (LED) was fabricated from the n-Ge/i-Ge/p-Si heterojunction structure grown by using Rapid Thermal Chemical Vapor Deposition (RTCVD). Ge buffer layers were grown at 350 °C with a thickness of ~110 nm in the first step. Then, high-temperature i-Ge layers were grown at 500 °C with a thickness of ~1.40 μm in the second step. The phosphorusdoped n-type Ge layers were grown at 500 °C with a thickness of ~0.61 μm in the third step. The surface morphology of the n-Ge/i-Ge layer was mirror like and the n-Ge/i-Ge layer was under a tensile strain of ~0.071%. Current-voltage characteristics of the PIN LED indicated a reasonable reverse saturation current of 140 μA at -1V. Electroluminescence characteristics showed a shift of the direct band gap to lower energies based on the depending of maximum peak position on the injection current. The direct band gap of the tensile-strained LEDs was found to be 0.746 eV.