Be incorporation and surface morphologies in homoepitaxial InP films

Abstract

We have studied the mechanism of Be incorporation in InP homoepitaxial films grown by metalorganic molecular beam epitaxy. The actual Be concentration in the films reaches 1–2×1019 cm−3 while the hole concentration saturates at a lower value ■∼2×1018 cm−3 in our case). The measured lattice mismatch between film and substrate depends both on growth temperature and Be flux. The resulting changes in morphology suggest that the excess Be forms microclusters in the films grown at higher temperatures—due to the higher surface mobility, leading to the growth of oval defects. Be rejection to the surface is also observed. The surfaces of samples with no cap layer present a granulation which may be related to the formation of a new phase like Be3P2.

Evidence of Be3P2 formation during growth of Be-doped phosphorus-based semiconductor compounds

“…Beryllium is a commonly used shallow acceptor for III-V semiconductor layers grown by molecular beam epitaxy ͑MBE͒ and chemical beam epitaxy ͑CBE͒ due to its high vapor pressure, close to unity sticking coefficient and low memory effects. However, for large concentrations, Be causes surface degradation 1,2 and, at least for phosphorus compounds, a small reduction in lattice parameter 3 as well as a reduction in the intensity and broadening of x-ray diffraction peak ͑rocking curve͒ measurements. In some cases, this effect is so large that it is not possible to consider the layer as crystalline.…”

“…A similar behavior was observed for the XRD of heavily Be-doped InP samples. 3 In that work, the difference between the atomic radii of Be and In was considered as the cause of the compression. For the mismatch values and Be concentrations considered here, however, this explanation does not seem realistic.…”

Strong spatial beryllium doping selectivity on InGaP layers grown on pre-patterned GaAs substrates by chemical beam epitaxy

“…Specifically for CBE, the behavior of Be is not well understood. For large impurity concentration and for the growth over (0 0 1) planar substrates, beryllium causes surface degradation [3,4] and, at least for phosphorus compounds, a small reduction in lattice parameter is observed [5], that is shown to be related to the formation of Be 3 P 2 clusters [6]. Also, a reduction in beryllium doping efficiency is observed as the growth temperature increases from 500 C to 540 C. Associated with the reduction in beryllium doping efficiency, it is always observed surface morphology degradation by atomic force microscopy and a direct relationship to an increased electrochemical etching pit density [7].…”