Some properties of carbon-doped GaAs using carbon tetrabromide in solid-source molecular beam epitaxy

Abstract

Heavily carbon-doped (C-doped) GaAs epitaxial films with hole concentration up to 1.86×10 20 cm −3 have been grown using carbon tetetrabromide (CBr 4) as dopant source in solid-source molecular beam epitaxy (SSMBE). The hole concentration decreases at concentration beyond 1.86×10 20 cm −3 due to compensation by carbon–carbon (C–C) pairs. At room temperature, the C-doped samples showed mobility of 77–60 cm 2/V s at hole concentration of 2.79×10 19–1.09×10 20 cm −3, respectively, comparable to samples doped with beryllium (Be). Low temperature (4 K) photoluminescence (PL) measurements show a reduction in band gap and broadening of the PL spectrum following increase in the doping concentration. The main PL peak shifts from ∼1.480 eV at concentration of 1.02×10 19 cm −3 to ∼1.452 eV at 6.95×10 19 cm −3. Variable temperature PL measurements show the existence of two peaks, which could arise from conduction band (CB) to heavy hole (HH) valence band and CB to light hole (LH) valence band transitions. Doping pulses created using CBr 4 flux resulted in abrupt transitions in the C-doping profile. Good agreement between the atomic concentration measured by secondary ion mass spectroscopy (SIMS) and the hole carrier concentration measured by Hall effect was observed up to doping level of 1.6×10 20 cm −3.