Heavily carbon-doped GaAs layers prepared by low-energy ion-beam impingement during molecular beam epitaxy

Low-energy (170 eV) C⁺ ion-beam doping during molecular beam epitaxy of GaAs was carried out using a combined ion beam and molecular beam epitaxy (CIBMBE) system. Incorporated C atoms were both electrically and optically well-activated as acceptors with doping levels up to 4 × 10¹⁹ cm^-3 in the as-grown condition. In low temperature (2 K) photoluminescence (PL) spectra, C-related specific emissions were clearly observed, indicating good quality of the films. To understand the advantages of low-energy process by CIBMBE, film quality and the rate of C activation were compared with those obtained from 400 keV hot implantation of C at substrate temperatures up to 600°C. Through Raman scattering, 2 K PL and Hall effect measurements, it was found that the use of a low-energy C⁺ ion beam offers advantages such as low damage doping and good activation rate of incorporated C atoms.