Optical and electrical properties of heavily carbon-doped GaAs fabricated by high-energy ion-implantation

High-energy (400 keV) implantation of carbon (C) ions was made into LEC-GaAs substrates with C concentration ([C]) of 1019--1022 cm-3. 2 K photoluminescence (PL) and Hall effect measurements indicated that activation rate of C in LEC GaAs is both optically and electrically extremely low even after furnace-annealing at 850 C for 20 min. For [C] = 1 x 1022 cm-3, two novel strong emissions were obtained and PL measurements as a function of excitation power and sample temperature suggested that the two emissions one at 1.485 eV and the other at 1.305 eV should reflect the formation of a new alloy between GaAs and C. Dual implantation of C+ and Ga+ ions was carried out to improve the activation or substitution rate. The authors found that nearly 90% activation rate can be achieved for C dose of 2.2 x 1013 cm-2