Optical and electrical studies of liquid-encapsulated Czochralski semi-insulating GaAs with different carbon concentrations

Abstract

The effects of the presence of carbon over a range of ~1014–1016 cm−3, in liquid-encapsulated Czochralski-grown semi-insulating GaAs have been studied using Fourier-transform infrared (FTIR), photoluminescence spectroscopy, photo-induced transients spectroscopy (PITS), and temperature-dependent Hall-effect measurements. The concentration of the carbon impurity was determined from the absorption line at 582.5 cm−1 on the spectra. From photoluminescence measurements in the temperature range of 4–30 K, the decay signal was found to consist of two parts: the initial decay obeying an exponential behaviour with an activation energy of 15 meV and the subsequent decay obeying a power law of the form t−p with the values of p ranging from 1.4 to 3.5. Results from PITS measurements revealed a broad peak at about 240 K (t2 − t1 = 20 ms; t1/t1 = 5), which could be due to the formation of a free As vacancy or its complexes. The intensity of the EL2 family of emission peaks was directly dependent on the water content of the boric oxide encapsulant used during the growth process. Mobility and resistivity of the samples were also measured and tabulated.