Defect luminescence in heavily Si-doped n- and p-type GaAs

We study the photoluIninescence(PL) and the photoconductivity spectra of Si-doped n- and p-GaAs grown by using liquid phase epitaxy. The defect-related PL peak observed around 1.367 eV in the p-epilayer is attributed to recombination between two states of a complex defect involving an As vacancy and a Si acceptor. This can be interpreted in terms of a configurational coordinate diagram. From this model, the vibrational energy of the defect is calculated as 26 meV by fitting the half width of the peak. The attribution is confirmed by investigating the evolution of the PL spectra in heavily Si-doped p-type samples having a doping gradient in the growth direction. The origins of the other PL peaks are also briefly discussed.