Near band-gap photoluminescence of the MOCVD-grown heavily Si-doped GaAs

Abstract

The luminescence of Si-doped GaAs with electron concentration up to 2.1 x 10'9 cm-3 is investigated. For the epitaxial layers with electron concentration less than 1 x 10'8 cm-3 the donor-acceptor pair luminescence was found to dominate, while at greater concentrations the indirect free electron transitions to the shallow acceptors prevail. The dependence of the luminescence spectra on the doping level was found to be different for two groups of layers. For the first group the spectra shifted to higher energies with increasing electron concentration in agreement with calculations of the Moss-Burstein effect, while for the second group there was almost no shift of the spectra up to n = 2.1 x 1019 cm-3. The measurements of luminescence excitation spectra have shown that the Fermi level is stabilised for the latter group of layers some 40-60 meV above the bottom of the conduction band. The presence of resonant levels in the conduction band of GaAs:Si was included to explain the Fermi-level stabilisation.

Determination of optical constants of n- and p-type GaAs as a function of carrier concentration

“…At the band edge, E 0 , the effect of doping is similar in both n-and p-type GaAs: as doping increases, the band edge broadens and shifts to a higher energy. This effect has previously been observed for n-type GaAs 25,26 but others report the bandgap narrowing with increased doping 27 . Bandgap shrinkage has also been observed p-type GaAs 28 .…”

H$_{2}$-diluted precursors for GaAs doping in chemical beam epitaxy

“…For the Si-doped samples, we observe the (e,A 0 ) transition together with a second transition at a higher energies. This second transition, assigned to bandto-band recombination (B,B) [37], blue shifts from 1.51 to 1.56 eV and broadens as the Si concentration increases from 7.8 × 10 17 to 8.3 × 10 18 cm −3 . Since GaAs becomes degenerated at 12 K for Si concentrations above 2×10 18 cm −3 , the broadening and blue-shift of the (B,B) transition is explained in terms of the Burstein-Moss effect [37].…”

“…This second transition, assigned to bandto-band recombination (B,B) [37], blue shifts from 1.51 to 1.56 eV and broadens as the Si concentration increases from 7.8 × 10 17 to 8.3 × 10 18 cm −3 . Since GaAs becomes degenerated at 12 K for Si concentrations above 2×10 18 cm −3 , the broadening and blue-shift of the (B,B) transition is explained in terms of the Burstein-Moss effect [37]. Such an evolution of the (B,B) transition with increasing Si doping level is characteristic of GaAs:Si layers regardless of the growth technique [37,38].…”

“…Since GaAs becomes degenerated at 12 K for Si concentrations above 2×10 18 cm −3 , the broadening and blue-shift of the (B,B) transition is explained in terms of the Burstein-Moss effect [37]. Such an evolution of the (B,B) transition with increasing Si doping level is characteristic of GaAs:Si layers regardless of the growth technique [37,38].…”