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 o f GaAs was carried out using a combined ion beam and molecular beam ep itaxy (CIBMBE) system, Incorporated C atoms were both electrically and optically well-activated as accepters with doping levels up to 4X10(1 9) cm(-3) in the as-grown condition. In low temperature (2 K) photolum inescence (PL) spectra, C-related specific emissions were clearly obse rved, indicating good quality of the films. To understand the advantag es of low-energy process by CIBMBE, film quality and the rate of C act ivation were compared with those obtained from 400 keV hot implantatio n of C at substrate temperatures up to 600 degrees C. Through Raman sc attering, 2 K PL and Hall effect measurements, it was found that the u se of a low-energy C+ ion beam offers advantages such as low damage do ping and good activation rate of incorporated C atoms.