High Temperature (77–300 K) Photo- and Electroluminescence in Si/Si_1-xGe_x Heterostructures

Abstract

In this study, we introduce a thin nickel interlayer to enhance the phase separation and silicon nanocrystal (Si-NC) growth in Si-rich silica films. Through TEM analysis, it is observed that the Si-NC density in the sample with a Ni interlayer is 2.6 times higher than that of the sample without Ni after high temperature annealing. The photoluminescence (PL) spectrum of the sample with a Ni interlayer is 2-5 times stronger than the one without Ni according to different silicon excess. By analysing the samples after rapid thermal annealing (RTA) with Fourier transform infrared absorption (FTIR), we find that nickel can induce phase separation in Si-rich silica films during annealing. Thermodynamic and kinetic analysis indicates a reduction of 31.4 kJ mol −1 in the Si-NC nucleation activation free energy by adding the nickel interlayer, which subsequently results in higher Si-NC density.

Photoinduced infrared spectroscopy of bound-to-bound and bound-to-continuum transitions in SiGe/Si quantum wells

“…Both the s-and p-polarized photo-induced intersubband absorptions vanish at room temperature for quantum wells with less than 30% germanium. This quenching is similar to that observed for photoluminescence and is attributed to the escape probability of the carriers from the well and to the different recombination times in the Si and SiGe layers [9]. In order to circumvent this problem, the germanium concentration has to be increased.…”

Numerical simulation of the temperature dependence of photoluminescence in strained-Si1?xGex/Si heterostructures

“…sharply decreasing intensity at elevated temperature) has been observed by several other groups [-6-8]. We have previously presented a simple model of this effect [9] in which we assumed no band bending, flat quasi-fermi levels, constant effective carrier lifetimes, Maxwell-Boltzmann statistics, and a radiative lifetime independent of temperature. The validity of these assumptions will be addressed later.…”

“…Most of the early work in this area was performed at very low temperatures (2-10 K) [1][2][3]. More recently, and motivated by the desire for a Si-based room temperature IR emitter [4,5], there has been interest in the temperature dependence of the PL intensity [6][7][8][9][10]. We previously have reported clear evidence that the luminescence efficiency of high quality strained-Si~ _~Gex/Si heterostructures at high temperature is controlled by recombination at the top Si surface rather than by bulk Si~ _xGex or Si properties and that proper surface passivation can increase the room temperature Si~ xGex PL by over an order of magnitude.…”

Silicon-germanium heterostructures ? advanced materials and devices for silicon technology

“…The process of adding Ge to Si which brings the bandgap down to the wavelength for fibre-optic transmission (1.3 to 1.55 gm), is also believed to relax the momentum conservation rule by virtue of the random positioning of the Ge atoms in the Si lattice [77]. This might be responsible for the significant photo and electroluminescence intensities observed at near-bandgap energies and at temperatures up to 300 K [78,79]. Theoreticians and experimentalists now agree that new band structures, quite different from those of bulk Si or Ge can be created in a Sin/Gem short-period superlattice (SPSL).…”